add copy external button

app/src/main/res/values/strings.xml

@@ -10,5 +10,6 @@
     <string name="preference_load_automatically">PreferenceLoadAutomatically</string>
     <string name="preference_load_automatically_name">Automatically launch</string>
     <string name="preference_load_automatically_description">Launches the game after a second-long delay.</string>
+    <string name="preferences_copy_external_button">Copy external files directory</string>
     <string name="title_activity_settings">SettingsActivity</string>
 </resources>