requestPermissions method
Convenience method checking browser notification support,
wrapper for Dart's native JS notification Notification.requestPermission().
Returns true if response matches 'granted'.
See: https://developer.mozilla.org/en-US/docs/Web/API/Notification/requestPermission_static
Implementation
@override
Future<bool> requestPermissions() {
// TODO: implement requestPermissions
throw UnimplementedError();
}