sendSMS method
void
sendSMS()
Implementation
void sendSMS() async {
await Firebase.initializeApp();
await FirebaseAuth.instance.verifyPhoneNumber(
phoneNumber: phoneNumber,
verificationCompleted: verificationCompleted,
verificationFailed: verificationFailed,
codeSent: smsCodeSent,
codeAutoRetrievalTimeout: onRetrievalTimeout,
timeout: Duration(seconds: 60),
);
}