Set default FCM notifications icons

android/app/src/main/AndroidManifest.xml

@@ -48,6 +48,11 @@
             android:name="flutterEmbedding"
             android:value="2" />
 
+        <!-- Default Firebase push notifications icons -->
+        <meta-data
+            android:name="com.google.firebase.messaging.default_notification_icon"
+            android:resource="@drawable/ic_notifications" />
+
         <activity
             android:name=".MainActivity"
             android:configChanges="orientation|keyboardHidden|keyboard|screenSize|locale|layoutDirection|fontScale|screenLayout|density|uiMode"