Add more Info to the wiki about Notification Icons

[sashthecash]

If you are using the Notification composer like us to send Notifications you will not be able to specify a custom Notification Icon in the Payload. To still make use of your packaged Icons and not have a blank white square on your Notifications you have to add this to the Manifest section of your descriptor (inside <application>):

<meta-data
    android:name="com.google.firebase.messaging.default_notification_icon"
    android:resource="@drawable/your_icon_name" />

And the tint can be changed like this:

<meta-data 
    android:name="com.google.firebase.messaging.default_notification_color"
    android:resource="@color/google_blue" />

I'm not sure how to specify a custom color since we are sticking to the default which is white.

[marchbold]

Sure, I'll get this added to the documentation in the PushNotifications ANE on FCM, as it's not directly related to the CustomResources script.