Added comment on FCM.(get/set)BadgeNumber not being available on Android.

README.md

@@ -289,8 +289,8 @@ class App extends Component {
         FCM.getScheduledLocalNotifications().then(notif=>console.log(notif));
         FCM.cancelLocalNotification("UNIQ_ID_STRING");
         FCM.cancelAllLocalNotifications();
-        FCM.setBadgeNumber();
-        FCM.getBadgeNumber().then(number=>console.log(number));
+        FCM.setBadgeNumber();                                       // iOS only and there's no way to set it in Android, yet.
+        FCM.getBadgeNumber().then(number=>console.log(number));     // iOS only and there's no way to get it in Android, yet.
     }
 }
 ```