(Example Android): Add file support

This permission is needed in order for the app to be able to access files.

Signed-off-by: Victor Omondi <victor@slick.co.ke>

Author: vickz84259

examples/push_notifications/android/app/src/main/AndroidManifest.xml

@@ -1,5 +1,6 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
     package="com.talkjs.flutter_push_example">
+    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
    <application
         android:usesCleartextTraffic="true"
         android:label="push_notifications"