Add firebase module to upload docs to firebase.

This is also improving the security as the bot service account with
short lived tokens will be used for authentication with firebase
services.

Change-Id: Ice03e924d1405ea896ea76381ef7efabc9d5c192
Bug: https://github.com/flutter/flutter/issues/60646
Reviewed-on: https://flutter-review.googlesource.com/c/recipes/+/7380
Reviewed-by: Keyong Han <keyonghan@google.com>
Commit-Queue: Godofredo Contreras <godofredoc@google.com>