feat: add danmuku plugin documentation and i18n setup guide

- Created a new documentation file for the danmuku plugin with code examples.
- Added comprehensive language settings documentation, including default languages, import instructions, and examples for adding and modifying languages.
- Updated the i18n documentation to reflect changes in language handling and provide clear examples for users.

docs/document/assets/en_start_i18n.md.Dn_-QNMz.lean.js

@@ -0,0 +1 @@
+import{_ as a,c as i,o as n,ak as l}from"./chunks/framework.xxfEszSJ.js";const g=JSON.parse('{"title":"Language Settings","description":"","frontmatter":{},"headers":[],"relativePath":"en/start/i18n.md","filePath":"en/start/i18n.md","lastUpdated":1764426402000}'),e={name:"en/start/i18n.md"};function p(t,s,h,r,k,E){return n(),i("div",null,s[0]||(s[0]=[l("",14)]))}const c=a(e,[["render",p]]);export{g as __pageData,c as default};