Link to Github contribution guide from main README

Stopgap until we can figure out a permanent solution via Copybara

Test: N/A docs changes only (view on Github!)
Change-Id: I8ad08e1583e8bf8a759d2235bdac7732b9b892f8

diff --git a/README.md b/README.md
index 81ba264..6d4ba4a 100644
--- a/README.md
+++ b/README.md

@@ -9,6 +9,11 @@
 You can learn more about using it from [Android Jetpack landing page](https://developer.android.com/jetpack).
 
 # Contribution Guide
+
+For contributions via GitHub, see the [GitHub Contribution Guide](CONTRIBUTING.md).
+
+Note: The contributions workflow via GitHub is currently experimental - only contributions to [Room](room) and [Workmanager](work) are being accepted at this time.
+
 ## Code Review Etiquette
 When contributing to Jetpack, follow the [code review etiquette](code-review.md).