feat: 增加动态设置字幕偏移功能，更新相关文档

packages/artplayer-vitepress/docs/advanced/property.md

@@ -964,4 +964,27 @@ art.on('ready', () => {
         column: 10,
     };
 });
+```
+
+## `subtitleOffset`
+
+-   Type: `Setter/Getter`
+-   Parameter: `Number`
+
+动态设置字幕偏移
+
+<div className="run-code">▶ Run Code</div>
+
+```js
+var art = new Artplayer({
+	container: '.artplayer-app',
+	url: '/assets/sample/video.mp4',
+    subtitle: {
+        url: '/assets/sample/subtitle.srt',
+    },
+});
+
+art.on('ready', () => {
+    art.subtitleOffset = 1;
+});
 ```