Native touch events (#42)

* add webrtc touch events.

* bind touch events to overlay.

* we care only for changed touches.

* switch to int32.

* pressure uint16.

* add implicit control.

* add touch to controls.

* fix iteration of changedTouches.

* switch pressure to uint8.

* convert force to pressure.

* add hasTouchEvents.

* add touch_events to state.

* bind touch or gesture handler on demand.

* remove duplicate gesture detach.

src/page/components/events.vue

@@ -334,6 +334,10 @@
           />
         </td>
       </tr>
+      <tr>
+        <th>control.touch_events</th>
+        <td>{{ neko.state.control.touch_events ? 'backend supports' : 'backend does not support' }}</td>
+      </tr>
       <tr>
         <th rowspan="2">control.host_id</th>
         <td>{{ neko.state.control.host_id }}</td>