Add default button to vibration/volume settings dialog

Change-Id: I7beb4517314efdefeb47d91b14a6b02c3075c19f
diff --git a/java/res/values/strings.xml b/java/res/values/strings.xml
index 5c54427..fd7aac4 100644
--- a/java/res/values/strings.xml
+++ b/java/res/values/strings.xml
@@ -376,4 +376,7 @@
     <string name="prefs_keypress_vibration_duration_settings">Keypress vibration duration settings</string>
     <!-- Title of the settings for keypress sound volume -->
     <string name="prefs_keypress_sound_volume_settings">Keypress sound volume settings</string>
+
+    <!-- Title of the button to revert to the default value of the device in the settings dialog [CHAR LIMIT=15] -->
+    <string name="button_default">Default</string>
 </resources>