Additional firebase testing updates.

client/public/firebase-messaging-sw.js

@@ -42,3 +42,8 @@ self.addEventListener("notificationclick", function (event) {
   // ...
   console.log("SW notificationclick", event);
 });
+
+self.addEventListener("message", (message) => {
+  console.log("Push from SW", message);
+//   registration.showNotification("Push from SW" + JSON.stringify(message.data));
+});