Add more instructions (#76)
Add more instructions (#76)

Adding the Google sign-in dependency instructions.
firebase/flutterfire,firebase/flutterfire,googleads/googleads-mobile-flutter,firebase/flutterfire,firebase/flutterfire,firebase/flutterfire,googleads/googleads-mobile-flutter,firebase/flutterfire,googleads/googleads-mobile-flutter,firebase/flutterfire,firebase/flutterfire,googleads/googleads-mobile-flutter,firebase/flutterfire,firebase/flutterfire