Mention dnd on IE touch devices in known issues (#13612)

Change-Id: I15297c2d0862f3b8c0c5603b06f6e37706872752

WebContent/release-notes.html

                 Firefox and streaming or long polling.
                 (<a href="http://dev.vaadin.com/ticket/13578">#13578</a>)
             </li>
+            <li>Drag'n'drop in a Table doesn't work on touch devices running
+                Internet Explorer (Windows Phone, Surface)
+                (<a href="http://dev.vaadin.com/ticket/13737">#13737</a>)
+            </li>
         </ul>
 
         <h3 id="limitations">Limitations</h3>