README says this repository is closed

Author: wardbell

README.md

@@ -1,3 +1,15 @@
+# This angular.io documentation repository is closed
+
+**Please do not add issues or pull requests to this repo.** 
+We are no longer making changes to documentation in this repository.
+We will no longer process new issues or PRs and we will close them automatically.
+
+**Please post new [issues](https://github.com/angular/angular/issues) and [pull requests](https://github.com/angular/angular/pulls) to the content folder in [https://github.com/angular/angular/tree/master/aio/content](https://github.com/angular/angular/tree/master/aio/content)**.
+
+Be sure to prefix your issue/PR title with "**docs(aio):**"
+
+<hr>
+
 # Angular.io
 [![Build Status][travis-badge]][travis-badge-url]