checkSupport method
Checks whether the current device and SIM card(s) support Firebase Phone Number Verification (PNV).
This is a lightweight, consent-free pre-check. Apps should call this
before attempting getVerifiedPhoneNumber so that unsupported
devices/carriers can fall back to a traditional SMS OTP flow (e.g. via
firebase_auth) without ever showing the PNV consent sheet.
Implementation
Future<bool> checkSupport() {
throw UnimplementedError('checkSupport() has not been implemented.');
}