Move 'use strict' to file level

Change-Id: I1f0dae4aa168e77c112bcd3688c98b84e4ce5f36
diff --git a/dev/js/src/selectMenu/item.js b/dev/js/src/selectMenu/item.js
index 3bd1406..b2ac071 100644
--- a/dev/js/src/selectMenu/item.js
+++ b/dev/js/src/selectMenu/item.js
@@ -1,3 +1,5 @@
+"use strict";
+
 define(['menu/item'], function (itemClass) {
   /**
    * Menu item for select menus.