Update README to mention web support (#1552)
Update README to mention web support (#1552)

* Update README to mention web support
firebase/flutterfire,firebase/flutterfire,firebase/flutterfire,googleads/googleads-mobile-flutter,googleads/googleads-mobile-flutter,firebase/flutterfire,googleads/googleads-mobile-flutter,firebase/flutterfire,googleads/googleads-mobile-flutter,firebase/flutterfire,firebase/flutterfire,firebase/flutterfire,firebase/flutterfire,firebase/flutterfire