Upgrade versions in FCM service worker (#382)

* Upgrade versions in FCM service worker

* Add comment telling users to use latest

Author: dlarocque

messaging/service-worker.js

@@ -10,8 +10,9 @@ function initInSw() {
   // Give the service worker access to Firebase Messaging.
   // Note that you can only use Firebase Messaging here. Other Firebase libraries
   // are not available in the service worker.
-  importScripts('https://www.gstatic.com/firebasejs/8.10.1/firebase-app.js');
-  importScripts('https://www.gstatic.com/firebasejs/8.10.1/firebase-messaging.js');
+  // Replace 10.13.2 with latest version of the Firebase JS SDK.
+  importScripts('https://www.gstatic.com/firebasejs/10.13.2/firebase-app-compat.js');
+  importScripts('https://www.gstatic.com/firebasejs/10.13.2/firebase-messaging-compat.js');
 
   // Initialize the Firebase app in the service worker by passing in
   // your app's Firebase config object.