Add README (ocaml#9)

Add README

README.md

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+# OCaml-LSP
+
+This project contains an implementation of an LSP server for OCaml and a
+standalone implementation of the LSP protocol.
+
+## Installation
+
+We recommend to install the server via a project such as
+[opam](http://github.com/ocaml/opam) or [esy](https://github.com/esy/esy).
+
+### Opam
+
+To install the lsp server in a particular opam switch:
+
+```
+$ opam install ocaml-lsp-server
+```
+
+Note that you will need to run install the lsp server in every switch where
+you'd like to use it.
+
+### Source
+
+This project uses submodules to handle dependencies. This is done so that users
+who install ocaml-lsp-server into their sandbox will not share constraints on
+the same dependencies that ocaml-lsp-server is using.
+
+```
+$ git clone --recurse-submodules http://github.com/ocaml/ocaml-lsp.git
+$ cd ocaml-lsp
+$ dune build
+```
+
+## Tests
+
+## Relationship to Other Tools
+
+The lsp server uses merlin under the hood, but users are not required to have
+merlin installed. We vendor merlin because we currently heavily depend on some
+implementation details of merlin that make infeasible to upgrade the lsp server
+and merlin independently.
+
+## History
+
+The implementation of the lsp protocol itself was taken from [facebook's
+hack](https://github.com/facebook/hhvm/blob/master/hphp/hack/src/utils/lsp/lsp.mli)
+
+Previously, this lsp server was a part of merlin, until it was realized that the
+lsp protocol covers a wider scope than merlin.