Add Android setup step

OneSignalExample/Assets/OneSignal/README.md

@@ -120,6 +120,12 @@ After building in Unity and exporting the XCode project follow these steps:
 6. **App Groups** should now be provisioned for you going forward for your iOS bundle id, even on clean builds.
 
 ### Android
+1. From the Unity Editor, navigate to **Edit > Project Settings > Player** and click the **Android** settings tab.
+2. Expand **Publishing Settings** and enable:
+   - Custom Main Gradle Template
+   - Custom Gradle Properties Template
+3. Navigate to **Assets > External Dependency Manager > Android Resolver > Force Resolve** and resolve your Android dependencies.
+
 Most of the Android setup was already handled during installation!
 
 The only thing remaining is to setup your own notification icons. You can do this be replacing the example icons located at `Assets/Plugins/Android/OneSignalConfig.plugin`