enhance UI on palm devices

Author: mika

src/pages/ui-control.html

@@ -123,6 +123,12 @@
             <div class="op-btn arraw">
               <kbd data-key-code="39">→</kbd>
             </div>
+            <div class="op-btn">
+              <kbd data-key-code="46">Delete</kbd>
+            </div>
+            <div class="op-btn">
+              <kbd data-key-code="13">Enter</kbd>
+            </div>
           </div>
         </div>
       </div>