Add read me file to explain where the code can be found.

Bug: 240287941
Test: read the file!
Change-Id: Ib622575e76b220340bad79f9603591255f1e3a14
diff --git a/ReadMe.txt b/ReadMe.txt
new file mode 100644
index 0000000..c37d14c
--- /dev/null
+++ b/ReadMe.txt
@@ -0,0 +1,3 @@
+This apk was built with the code released to aosp on June 23, 2022.
+To fetch and build the code, please follow the steps described here:
+https://source.android.com/docs/devices/automotive/unbundled_apps/integration