Add initial docs 📝

Most of these docs have been copy pasted from
https://github.com/tektoncd/pipelines.

These docs currently refer to code and config that doesn't yet exist,
but point us the direction of a great first step, which would be to make
it so that the info in these docs is correct (e.g. we can build and
deploy a controller, even if it doesn't do anything, etc.).

These are the docs required at https://github.com/tektoncd/community/blob/master/process.md#project-requirements

.github/issue-template.md

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+---
+name: Issue Template
+about: Template for both bug reports and feature requests
+---
+
+# Expected Behavior
+
+# Actual Behavior
+
+# Steps to Reproduce the Problem
+
+1.
+2.
+3.
+
+# Additional Info

.github/pull_request_template.md

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+# Changes
+
+<!-- 🎉🎉🎉 Thank you for the PR!!! 🎉🎉🎉 -->
+
+<!-- Describe your changes here- ideally you can get that description straight from
+your descriptive commit message(s)! -->
+
+# Submitter Checklist
+
+These are the criteria that every PR should meet, please check them off as you
+review them:
+
+- [ ] Includes [tests](https://github.com/tektoncd/community/blob/master/standards.md#principles) (if functionality changed/added)
+- [ ] Includes [docs](https://github.com/tektoncd/community/blob/master/standards.md#principles) (if user facing)
+- [ ] Commit messages follow [commit message best practices](https://github.com/tektoncd/community/blob/master/standards.md#commit-messages)
+
+_See [the contribution guide](https://github.com/tektoncd/triggers/blob/master/CONTRIBUTING.md) for more details._
+
+# Release Notes
+
+```
+Describe any user facing changes here, or delete this block.
+
+Examples of user facing changes:
+- API changes
+- Bug fixes
+- Any changes in behavior
+
+```

CONTRIBUTING.md

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+# Contributing to Tekton Triggers
+
+Welcome to the Tekton Triggers project! Thanks for considering contributing to
+our project and we hope you'll enjoy it :D
+
+**All contributors must comply with
+[the code of conduct](./code-of-conduct.md).**
+
+To get started developing, see our [DEVELOPMENT.md](./DEVELOPMENT.md).
+
+In [the community repo](https://github.com/tektoncd/community) you'll find info
+on:
+
+- [Contacting other contributors](https://github.com/tektoncd/community/blob/master/contact.md)
+- [Development standards](https://github.com/tektoncd/community/blob/master/standards.md)
+  around
+  [principles](https://github.com/tektoncd/community/blob/master/standards.md#principles),
+  [commit messages](https://github.com/tektoncd/community/blob/master/standards.md#commit-messages)
+  and
+  [code](https://github.com/tektoncd/community/blob/master/standards.md#coding-standards)
+- [Processes](https://github.com/tektoncd/community/blob/master/process.md) like
+  [finding something to work on](https://github.com/tektoncd/community/blob/master/process.md#finding-something-to-work-on),
+  [proposing features](https://github.com/tektoncd/community/blob/master/process.md#proposing-features),
+  [reviews](https://github.com/tektoncd/community/blob/master/process.md#reviews)
+  and
+  [becoming an OWNER](https://github.com/tektoncd/community/blob/master/process.md#owners)
+
+You can find details on our automation infrastructure in
+[the plumbing repo](https://github.com/tektoncd/plumbing).
+
+For more Triggers specific guidelines, see:
+
+- [The Tekton Triggers ZenHub project](#zenhub-project)
+
+See also [the Tekton Pipelines roadmap](http://github.com/tektoncd/pipeline/blob/master/roadmap-2019.md)
+
+## ZenHub project
+
+You can see project details (including a burndown, issues in epics, etc.) on
+[our ZenHub board](https://app.zenhub.com/workspaces/triggers-5d0ebce343e42a09a0a4a826).
+
+To see this board, you must:
+
+- Ask [an OWNER](OWNERS) via
+  [slack](https://github.com/tektoncd/community/blob/master/contact.md#slack)
+  for an invitation
+- Add [the ZenHub browser extension](https://www.zenhub.com/extension) to see
+  new info via GitHub (or just use zenhub.com directly)

DEVELOPMENT.md

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+# Tekton Triggers Development Guide
+
+## Getting started
+
+1. [Ramp up on kubernetes and CRDs](#ramp-up-on-crds)
+1. [Ramp Tekton Pipelines](#ramp-up-on-tekton-pipelines)
+1. Create [a GitHub account](https://github.com/join)
+1. Setup
+   [GitHub access via SSH](https://help.github.com/articles/connecting-to-github-with-ssh/)
+1. [Create and checkout a repo fork](#checkout-your-fork)
+1. Set up your [shell environment](#environment-setup)
+1. Install [requirements](#requirements)
+1. [Set up a Kubernetes cluster](#kubernetes-cluster)
+1. [Configure kubectl to use your cluster](https://kubernetes.io/docs/tasks/access-application-cluster/configure-access-multiple-clusters/)
+1. [Set up a docker repository you can push to](https://github.com/knative/serving/blob/master/docs/setting-up-a-docker-registry.md)
+1. [Install Tekton Pipelines](#install-pipelines)
+1. [Install Tekton Triggers](#install-triggers)
+1. [Iterate!](#iterating)
+
+### Ramp up
+
+Welcome to the project!! You may find these resources helpful to ramp up on some
+of the technology this project is built on.
+
+#### Ramp up on CRDs
+
+This project extends Kubernetes (aka
+`k8s`) with Custom Resource Definitions (CRDSs). To find out more:
+
+- [The Kubernetes docs on Custom Resources](https://kubernetes.io/docs/concepts/extend-kubernetes/api-extension/custom-resources/) -
+  These will orient you on what words like "Resource" and "Controller"
+  concretely mean
+- [Understanding Kubernetes objects](https://kubernetes.io/docs/concepts/overview/working-with-objects/kubernetes-objects/) -
+  This will further solidify k8s nomenclature
+- [API conventions - Types(kinds)](https://github.com/kubernetes/community/blob/master/contributors/devel/sig-architecture/api-conventions.md#types-kinds) -
+  Another useful set of words describing words. "Objects" and "Lists" in k8s
+  land
+- [Extend the Kubernetes API with CustomResourceDefinitions](https://kubernetes.io/docs/tasks/access-kubernetes-api/custom-resources/custom-resource-definitions/)-
+  A tutorial demonstrating how a Custom Resource Definition can be added to
+  Kubernetes without anything actually "happening" beyond being able to list
+  Objects of that kind
+
+#### Ramp up on Tekton Pipelines
+
+- [Tekton Pipelines README](https://github.com/tektoncd/pipeline/blob/master/docs/README.md) -
+  Some of the terms here may make more sense!
+- Install via
+  [official installation docs](https://github.com/tektoncd/pipeline/blob/master/docs/install.md)
+  or continue though [getting started for development](#getting-started)
+- [Tekton Pipeline "Hello World" tutorial](https://github.com/tektoncd/pipeline/blob/master/docs/tutorial.md) -
+  Define `Tasks`, `Pipelines`, and `PipelineResources`, see what happens when
+  they are run
+
+### Checkout your fork
+
+The Go tools require that you clone the repository to the
+`src/github.com/tektoncd/triggers` directory in your
+[`GOPATH`](https://github.com/golang/go/wiki/SettingGOPATH).
+
+To check out this repository:
+
+1. Create your own
+   [fork of this repo](https://help.github.com/articles/fork-a-repo/)
+1. Clone it to your machine:
+
+```shell
+mkdir -p ${GOPATH}/src/github.com/tektoncd
+cd ${GOPATH}/src/github.com/tektoncd
+git clone [email protected]:${YOUR_GITHUB_USERNAME}/triggers.git
+cd triggers
+git remote add upstream [email protected]:tektoncd/triggers.git
+git remote set-url --push upstream no_push
+```
+
+_Adding the `upstream` remote sets you up nicely for regularly
+[syncing your fork](https://help.github.com/articles/syncing-a-fork/)._
+
+### Requirements
+
+You must install these tools:
+
+1. [`go`](https://golang.org/doc/install): The language Tekton Pipelines is
+   built in
+1. [`git`](https://help.github.com/articles/set-up-git/): For source control
+1. [`dep`](https://github.com/golang/dep): For managing external Go
+   dependencies. - Please Install dep v0.5.0 or greater.
+1. [`ko`](https://github.com/google/ko): For development. `ko` version v0.1 or
+   higher is required for `triggers` to work correctly.
+1. [`kubectl`](https://kubernetes.io/docs/tasks/tools/install-kubectl/): For
+   interacting with your kube cluster
+
+Your [`$GOPATH`] setting is critical for `ko apply` to function properly: a
+successful run will typically involve building pushing images instead of only
+configuring Kubernetes resources.
+
+## Kubernetes cluster
+
+Docker for Desktop using an edge version has been proven to work for both
+developing and running Pipelines. The recommended configuration is:
+
+- Kubernetes version 1.11 or later
+- 4 vCPU nodes (`n1-standard-4`)
+- Node autoscaling, up to 3 nodes
+- API scopes for cloud-platform
+
+To setup a cluster with GKE:
+
+1. [Install required tools and setup GCP project](https://github.com/knative/docs/blob/master/docs/install/Knative-with-GKE.md#before-you-begin)
+   (You may find it useful to save the ID of the project in an environment
+   variable (e.g. `PROJECT_ID`).
+
+1. Create a GKE cluster (with `--cluster-version=latest` but you can use any
+   version 1.11 or later):
+
+   ```bash
+   export PROJECT_ID=my-gcp-project
+   export CLUSTER_NAME=mycoolcluster
+
+   gcloud container clusters create $CLUSTER_NAME \
+    --enable-autoscaling \
+    --min-nodes=1 \
+    --max-nodes=3 \
+    --scopes=cloud-platform \
+    --enable-basic-auth \
+    --no-issue-client-certificate \
+    --project=$PROJECT_ID \
+    --region=us-central1 \
+    --machine-type=n1-standard-4 \
+    --image-type=cos \
+    --num-nodes=1 \
+    --cluster-version=latest
+   ```
+
+   Note that
+   [the `--scopes` argument to `gcloud container cluster create`](https://cloud.google.com/sdk/gcloud/reference/container/clusters/create#--scopes)
+   controls what GCP resources the cluster's default service account has access
+   to; for example to give the default service account full access to your GCR
+   registry, you can add `storage-full` to your `--scopes` arg.
+
+1. Grant cluster-admin permissions to the current user:
+
+   ```bash
+   kubectl create clusterrolebinding cluster-admin-binding \
+   --clusterrole=cluster-admin \
+   --user=$(gcloud config get-value core/account)
+   ```
+
+## Environment Setup
+
+To [run your controllers with `ko`](#install-triggers) you'll need to set these
+environment variables (we recommend adding them to your `.bashrc`):
+
+1. `GOPATH`: If you don't have one, simply pick a directory and add
+   `export GOPATH=...`
+1. `$GOPATH/bin` on `PATH`: This is so that tooling installed via `go get` will
+   work properly.
+1. `KO_DOCKER_REPO`: The docker repository to which developer images should be
+   pushed (e.g. `gcr.io/[gcloud-project]`). You can also run a local registry
+   and set `KO_DOCKER_REPO` to reference the registry (e.g. at
+   `localhost:5000/myimages`).
+
+`.bashrc` example:
+
+```shell
+export GOPATH="$HOME/go"
+export PATH="${PATH}:${GOPATH}/bin"
+export KO_DOCKER_REPO='gcr.io/my-gcloud-project-name'
+```
+
+Make sure to configure
+[authentication](https://cloud.google.com/container-registry/docs/advanced-authentication#standalone_docker_credential_helper)
+for your `KO_DOCKER_REPO` if required. To be able to push images to
+`gcr.io/<project>`, you need to run this once:
+
+```shell
+gcloud auth configure-docker
+```
+
+The user you are using to interact with your k8s cluster must be a cluster admin
+to create role bindings:
+
+```shell
+# Using gcloud to get your current user
+USER=$(gcloud config get-value core/account)
+# Make that user a cluster admin
+kubectl create clusterrolebinding cluster-admin-binding \
+  --clusterrole=cluster-admin \
+  --user="${USER}"
+```
+
+## Install Pipelines
+
+To install [Tekton Pipelines](https://github.com/tektoncd/pipeline) you can
+either:
+
+* [Install a released version](https://github.com/tektoncd/pipeline/blob/master/docs/install.md)
+* [Setup Tekton Pipelines for development](https://github.com/tektoncd/pipeline/blob/master/DEVELOPMENT.md)
+  (install and iterate from HEAD)
+
+## Iterating
+
+While iterating on the project, you may need to:
+
+1. [Install/Run Pipelines](#install-pipelines)
+1. [Install/Run Triggers](#install-triggers)
+1. Verify it's working by [looking at the logs](#accessing-logs)
+1. Update your (external) dependencies with: `./hack/update-deps.sh`.
+
+   **Running dep ensure manually, will pull a bunch of scripts deleted
+   [here](./hack/update-deps.sh#L29)**
+
+1. Update your type definitions with: `./hack/update-codegen.sh`.
+1. [Add new CRD types](#adding-new-types)
+1. [Add and run tests](./test/README.md#tests)
+
+To make changes to these CRDs, you will probably interact with
+(**Note this code doesn't yet exist!!**):
+
+- The CRD type definitions in
+  [./pkg/apis/triggers/alpha1](./pkg/apis/triggers/v1alpha1)
+- The reconcilers in [./pkg/reconciler](./pkg/reconciler)
+- The clients are in [./pkg/client](./pkg/client) (these are generated by
+  `./hack/update-codegen.sh`)
+
+### Install Triggers
+
+**Note: this is aspirational! We don't yet have any code or config to deploy,
+watch this space!**
+
+You can stand up a version of this controller on-cluster (to your
+`kubectl config current-context`):
+
+```shell
+ko apply -f config/
+```
+
+### Redeploy controller
+
+As you make changes to the code, you can redeploy your controller with:
+
+```shell
+ko apply -f config/controller.yaml
+```
+
+### Tear it down
+
+You can clean up everything with:
+
+```shell
+ko delete -f config/
+```
+
+## Accessing logs
+
+To look at the controller logs, run:
+
+```shell
+kubectl -n tekton-pipelines logs $(kubectl -n tekton-pipelines get pods -l app=tekton-triggers-controller -o name)
+```
+
+To look at the webhook logs, run:
+
+```shell
+kubectl -n tekton-pipelines logs $(kubectl -n tekton-pipelines get pods -l app=tekton-triggers-webhook -o name)
+```
+
+## Adding new types
+
+If you need to add a new CRD type, you will need to add:
+
+1. A yaml definition in [config/](./config)
+1. Add the type to the cluster roles in
+   [200-clusterrole.yaml](./config/200-clusterrole.yaml)