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-jassub.d.ts

@@ -34,5 +34,5 @@ declare const artplayerPluginJassub: (option: JassubOption) => (art: Artplayer)
 
 export default artplayerPluginJassub
 
-export = artplayerPluginJassub
-export as namespace artplayerPluginJassub;
+export = artplayerPluginJassub;
+export as namespace artplayerPluginJassub;