add vibration duration settings

Change-Id: I56a1a94df63160f367f866da759d7dd4fc428ed5
diff --git a/java/res/values/strings.xml b/java/res/values/strings.xml
index 2f591fd..a1c1a9f 100644
--- a/java/res/values/strings.xml
+++ b/java/res/values/strings.xml
@@ -343,4 +343,6 @@
 
     <!-- Title of an option for usability study mode -->
     <string name="prefs_usability_study_mode">Usability study mode</string>
+    <!-- Title of the settings for vibration duration -->
+    <string name="prefs_vibration_duration_settings">Vibration duration settings</string>
 </resources>