feat: add danmuku plugin documentation and i18n setup guide

- Created a new documentation file for the danmuku plugin with code examples.
- Added a comprehensive guide for language settings (i18n) including default languages, importing languages, adding new languages, and modifying existing languages.
- Included code snippets for initializing the Artplayer with different language configurations.

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;