add DEVELOPMENT.md

DEVELOPMENT.md

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+# Build and run `kcp`
+
+```
+go run ./cmd/kcp start
+```
+
+This will build and run your kcp server, and generate a kubeconfig in `.kcp/data/admin.kubeconfig` you can use to connect to it:
+
+```
+KUBECONFIG=.kcp/data/admin.kubeconfig
+kubectl api-resources
+```
+
+The kubeconfig configures two contexts, `user` (the default) and `admin`.
+Switch the default context to `admin` with the following command:
+
+```
+kubectl config use-context admin
+```
+
+# Build and run Cluster Controller
+
+First, be sure to define the Cluster CRD type:
+
+```
+kubectl apply -f config/cluster.example.dev_clusters.yaml
+```
+
+The Cluster Controller requires a `--syncer_image` to install on new clusters.
+To build this image and pass it to the Cluster Controller, you can use [`ko`](https://github.com/google/ko):
+
+```
+go run ./cmd/cluster-controller \
+    --syncer_image=$(ko publish ./cmd/syncer) \
+    --kubeconfig=.kcp/data/admin.kubeconfig
+```
+
+`ko publish` requires the `KO_DOCKER_REPO` env var to be set to the container image registry to push the image to (e.g., `KO_DOCKER_REPO=quay.io/my-user`).
+If you're using [KinD](https://kind.sigs.k8s.io), you can set `KO_DOCKER_REPO=kind.local` to publish to your local KinD cluster.