feat: add danmuku plugin and i18n setup documentation

- Created a new documentation file for the danmuku plugin with code examples.
- Added a new documentation file for language settings (i18n) with detailed instructions on language imports, default languages, and how to add or modify languages.

docs/assets/ts/artplayer-plugin-danmuku-mask.d.ts

@@ -21,5 +21,5 @@ declare const artplayerPluginDanmukuMask: (option?: Option) => (art: Artplayer)
 
 export default artplayerPluginDanmukuMask
 
-export = artplayerPluginDanmukuMask
-export as namespace artplayerPluginDanmukuMask;
+export = artplayerPluginDanmukuMask;
+export as namespace artplayerPluginDanmukuMask;