完成selector

docs/document/_sidebar.md

@@ -4,3 +4,4 @@
 -   [Events](/events)
 -   [Class](/class)
 -   [Libraries](/libraries)
+-   [Question](/question)

docs/document/question.md

@@ -0,0 +1,35 @@
+## Create selector in the controls
+
+Sometimes you need to customize the behavior of the selector, then you can add `selector` and `onSelect` properties when adding a control. At the same time, you can also perform custom operations by listening to the `selector` event
+
+[Run Code](/Question.selector)
+
+```js
+var art = new Artplayer({
+    container: '.artplayer-app',
+    url: '/assets/sample/video.mp4',
+    controls: [
+        {
+            position: 'right',
+            html: 'Subtitle 01',
+            selector: [
+                {
+                    name: 'Subtitle 01',
+                    url: '/assets/sample/subtitle.srt?id=1',
+                },
+                {
+                    name: 'Subtitle 02',
+                    url: '/assets/sample/subtitle.srt?id=2',
+                },
+            ],
+            onSelect: function (item) {
+                art.subtitle.switch(item.url, item.name);
+            },
+        },
+    ],
+});
+
+art.on('selector', function (item) {
+    console.info(item);
+});
+```