MainApplication.java setup for firebase

MainApplication.java

//...

import io.invertase.firebase.messaging.RNFirebaseMessagingPackage;
import io.invertase.firebase.notifications.RNFirebaseNotificationsPackage;

//...

protected List<ReactPackage> getPackages() {
  @SuppressWarnings("UnnecessaryLocalVariable")
  List<ReactPackage> packages = new PackageList(this).getPackages();
    //...
    packages.add(new RNFirebaseMessagingPackage());
    packages.add(new RNFirebaseNotificationsPackage());
  return packages;
}