update docs

docs/assets/example/index.js

@@ -1,6 +1,6 @@
 var art = new Artplayer({
     container: '.artplayer-app',
-    url: 'https://artplayer.org/assets/sample/video.mp4',
+    url: 'https://6169-aimu-7ggfmae4da13977b-1256594555.tcb.qcloud.la/template/video.mp4',
     title: 'One More Time One More Chance',
     poster: '/assets/sample/poster.jpg',
     volume: 0.5,
@@ -36,17 +36,14 @@ var art = new Artplayer({
                 {
                     default: true,
                     html: 'Custom setting 01',
-                    onSelect: function () {
-                        console.info('You clicked on the custom setting 01');
-                    },
                 },
                 {
                     html: 'Custom setting 02',
-                    onSelect: function () {
-                        console.info('You clicked on the custom setting 02');
-                    },
                 },
             ],
+            onSelect: function (item) {
+                console.info('You clicked on the custom setting', item.html);
+            },
         },
     ],
     contextmenu: [