Navigation Treeview Example Using Computed Properties: Editorial revi…

…sion to accessibility features

For issue #225, in examples/treeview/treeview-2/treeview-2a.html accessibility features section,
added brief description of purpose of custom focus indicator.

examples/treeview/treeview-2/treeview-2a.html

@@ -331,7 +331,7 @@ <h3 id="tree1">Foods</h3>
       <section>
         <h2>Accessibility Features</h2>
         <p>
-          The expandable nodes (parent items) in the tree have a custom focus and hover styling created using CSS focus and hover classes.
+          To make the focus indicator easier to see, the expandable nodes (parent items) in the tree have a custom focus and hover styling created using CSS focus and hover classes.
           To do this, focus, blur, mouseover, and mouseout events trigger application of classes to the <code>span</code> element that contains the visible label of the <code>treeitem</code>.
         </p>
       </section>