add deprecation message (#736)

* add deprecation message

* remove rest of readme

README.md

@@ -1,29 +1,8 @@
-# Deno Manual
+# (DEPRECATED) Deno Manual
 
-This repository is the official documentation for Deno, and it's available at:
-https://deno.land/manual
+This repository was formerly the home of the Deno manual, running at
+deno.land/manual. The instructions below describe how to run the doc site and
+preview changes.
 
-## Contributing
-
-1. Clone this project and `dotland` in the same parent folder:
-
-```
-git clone https://github.com/denoland/manual.git
-git clone https://github.com/denoland/dotland.git
-```
-
-2. Move into the `dotland` folder, and run the following command to start the
-   local `deno.land` website with the local manual contents:
-
-```
-cd dotland
-MANUAL_PATH=../manual deno task start
-```
-
-When opening a PR, make sure the code is formatted correctly. To format the
-code:
-
-1. Install Deno (https://deno.land/#installation)
-2. Run `deno fmt` at the root of this repository
-
-Before creating new pages, open an issue and discuss the proposed changes.
+**New contributions should be made to
+[docs.deno.com](https://github.com/denoland/deno-docs)**