Add backup key

src/googleplay/AndroidManifest.xml

@@ -25,6 +25,10 @@
 
     <application>
 
+        <meta-data
+            android:name="com.google.android.backup.api_key"
+            android:value="AEdPqrEAAAAI49v5bBusi_bq1bgLBB1LIsepNV0eBrFkQrBZkw" />
+
         <meta-data
             android:name="com.google.android.gms.version"
             android:value="@integer/google_play_services_version" />