Add keyboard controls to side-by-side demo

demos/side-by-side/index.html.in

@@ -40,6 +40,26 @@
                 <td>Rotate:</td>
                 <td>shift+drag (WebGL only)</td>
             </tr>
+            <tr>
+                <td>Brightness/contrast:</td>
+                <td><code>b</code>/<code>B</code>/<code>c</code>/<code>C</code> keys (WebGL only)</td>
+            </tr>
+            <tr>
+                <td>Hue/saturation:</td>
+                <td><code>h</code>/<code>H</code>/<code>s</code>/<code>S</code> keys (WebGL only)</td>
+            </tr>
+            <tr>
+                <td>Opacity:</td>
+                <td><code>o</code>/<code>O</code> keys</td>
+            </tr>
+            <tr>
+                <td>Visibility:</td>
+                <td><code>v</code>/<code>V</code> keys</td>
+            </tr>
+            <tr>
+                <td>Reset</td>
+                <td><code>0</code> key</td>
+            </tr>
         </table>
         <script src="@SRC@" type="text/javascript"></script>
     </body>