feat: add danmuku plugin documentation and i18n setup

- Created a new documentation file for the danmuku plugin with interactive code execution.
- Added comprehensive i18n setup instructions, including default language settings, language imports, and examples for adding and modifying languages.
- Introduced a test file to verify the integration of the danmuku plugin.

test/esm.test.js

@@ -0,0 +1,3 @@
+import artplayerPluginDanmuku from 'artplayer-plugin-danmuku'
+
+console.log(typeof artplayerPluginDanmuku)