Nativescript-plugin-firebase: Add ability to add scopes for GoogleAuthProvider

[romandragan]

Could we add an ability of adding scopes to the GoogleAuthProvider?

https://firebase.google.com/docs/auth/web/google-signin#handle_the_sign-in_flow_with_the_firebase_sdk

[EddyVerbruggen]

Thanks for asking - would you be able to link to the iOS and Android docs as well?

[romandragan]

@EddyVerbruggen, sure.

For Android we can use GoogleSignInOptions.Builder.requestScopes(..) function.

For iOS I believe we can use GIDSignIn.scopes property.

[EddyVerbruggen]

Thanks! Added the required code an docs.