Add README am: 3aeba4cab6 am: 591bf2432c am: f9cd093ca0 am: ec2af4c798 am: 87a4983a94

Original change: https://android-review.googlesource.com/c/platform/packages/apps/Messaging/+/2614297

Change-Id: I593ae2acc96d916e82ba48835810dcf016919216
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>
diff --git a/README b/README
new file mode 100644
index 0000000..15142ba
--- /dev/null
+++ b/README
@@ -0,0 +1,2 @@
+This app is not actively supported and the source is only available as a reference. This project will be removed from the source manifest sometime in the future.
+