title: Modify notification from FCM / onMessageReceived not called when app is in background
body: <p>I'm building an app in react native, and I attached <code>react-native-fcm</code> library to the code, in order to work with notification messages.</p>
  
  <p>I have two main problems:</p>
  
  <p>1) Notification from the <code>firebase</code> doesn't look like the ordinary notification messages: it's not appear with app icon, it doesn't popup and presented when the screen is closed.</p>
  
  <p>2) I wanted just to get the event of messaging, also here after reviewing the  library code, I saw that notification get to the function: <code>onMessageReceived</code> only if the app on foreground, like it say in the website.<br>
  But in the website I couldn't understand how to get the general event of catching notificaiton regardless to the appstate.
  I also tried to implement class that extends <code>FirebaseMessagingService</code>, and there the notification doesn't get to the <code>onMessageReceived</code> override at all.</p>