Add a deprecation notice to the checks plugin

Change-Id: I6db38861bf6d6bb69f536f382be35934b896010f

README.md

diff --git a/README.md b/README.md
index 3c514d2..0228756 100644
--- a/README.md
+++ b/README.md
@@ -1,4 +1,12 @@
-# Gerrit Code Review Checks Plugin
+# DEPRECATION NOTICE
+
+The Gerrit team at Google has decided to discontinue work on the
+checks plugin. The recommended solution is
+[https://gerrit-review.googlesource.com/Documentation/pg-plugin-checks-api.html](Checks
+UI) which surfaces results from an external CI/analysis system.
+
+
+# Gerrit Code Review Checks Plugin (DEPRECATED)
 
 This plugin provides a unified experience for checkers (CI systems, static
 analyzers, etc.) to integrate with Gerrit Code Review.