[skip ci] Update zip Readme for current platform support (#9691)

Author: paulb777

ReleaseTooling/Template/README.md

@@ -1,7 +1,8 @@
-# Firebase iOS SDKs
+# Firebase Apple SDKs
 
-This directory contains the full Firebase iOS distribution, packaged as
-static xcframeworks that can be integrated into your app.
+This directory contains the full Firebase Apple distribution, packaged as static
+xcframeworks that include support for the iOS, tvOS, macOS, and Catalyst
+platforms.
 
 # Integration Instructions