Add disclaimer to README (#28)

Author: samtstern

README.md

@@ -7,6 +7,13 @@ using Firebase tools to add great functions like cross-platform leaderboards!
 See the subdirectories for more information on how to incorporate a specific
 solution.
 
+## Status
+
+![Status: Experimental](https://img.shields.io/badge/Status-Experimental-blue)
+
+This repository is maintained by Googlers but is not a supported Firebase product. Issues here are answered by maintainers and other community members on GitHub on a best-effort basis.
+
+
 ## Solutions
 - [Cross Platform Leaderboard using Firebase Database](https://github.com/FirebaseExtended/unity-solutions/tree/master/Firebase_Leaderboard)
 - [Auto Sync with Remote Config](https://github.com/FirebaseExtended/unity-solutions/tree/master/Firebase_RemoteConfig)