feat: add danmuku plugin documentation and i18n setup guide

- Created a new documentation file for the danmuku plugin with code examples.
- Added comprehensive i18n setup instructions, including default language settings, language imports, and examples for adding and modifying languages.
- Updated the structure and content of the i18n documentation to enhance clarity and usability.

packages/artplayer-vitepress/docs/start/i18n.md

@@ -33,8 +33,8 @@ var art = new Artplayer({
 ::: code-group
 
 ```js [import]
-import id from 'artplayer/dist/i18n/id.js';
-import zhTw from 'artplayer/dist/i18n/zh-tw.js';
+import id from 'artplayer/i18n/id';
+import zhTw from 'artplayer/i18n/zh-tw';
 
 var art = new Artplayer({
     container: '.artplayer-app',
@@ -82,7 +82,7 @@ var art = new Artplayer({
 ## 修改语言
 
 ```js
-import zhTw from 'artplayer/i18n/zh-tw.js';
+import zhTw from 'artplayer/i18n/zh-tw';
 
 var art = new Artplayer({
     container: '.artplayer-app',