update example for v6

Examples/simple-fcm-client/app/PushController.js

 import React, { Component } from "react";
 
-import FCM, {FCMEvent} from "react-native-fcm";
+import FCM, {FCMEvent, RemoteNotificationResult, WillPresentNotificationResult, NotificationType} from "react-native-fcm";
 
 import firebaseClient from  "./FirebaseClient";