docs(firebase_auth): add steps for Email Link Authentication (#3943)
docs(firebase_auth): add steps for Email Link Authentication (#3943)

Flutter port of the 'sending' and 'link verification' process of this page https://firebase.google.com/docs/auth/android/email-link-auth
firebase/flutterfire,firebase/flutterfire,firebase/flutterfire,firebase/flutterfire,firebase/flutterfire,firebase/flutterfire,firebase/flutterfire,firebase/flutterfire,firebase/flutterfire,firebase/flutterfire