adding a Productivity app category

Author: tibbi

app/src/main/AndroidManifest.xml

@@ -14,6 +14,7 @@
     <application
         android:name=".App"
         android:allowBackup="true"
+        android:appCategory="productivity"
         android:icon="@mipmap/ic_launcher"
         android:label="@string/app_launcher_name"
         android:roundIcon="@mipmap/ic_launcher"