优化demo

docs/assets/example/backlight.js

@@ -3,8 +3,19 @@ var art = new Artplayer({
     container: '.artplayer-app',
     url: url + '/video/your-name.mp4',
     autoSize: true,
+    localVideo: true,
     moreVideoAttr: {
         crossOrigin: 'anonymous',
     },
+    controls: [
+        {
+            name: 'open',
+            position: 'right',
+            html: 'Local Video',
+            mounted: $open => {
+                art.plugins.localVideo.attach($open);
+            },
+        },
+    ],
     plugins: [artplayerPluginBacklight],
 });