feat: add Document Picture-in-Picture plugin for ArtPlayer

- Implemented the core functionality of the Document Picture-in-Picture plugin.
- Created main plugin file `artplayer-plugin-document-pip.js` with support for opening and closing the PIP window.
- Added legacy support in `artplayer-plugin-document-pip.legacy.js`.
- Defined plugin options in `package.json` and included necessary metadata.
- Developed the main logic in `src/index.js`, including style copying and event handling.
- Created TypeScript definitions in `types/artplayer-plugin-document-pip.d.ts` for better type safety.

docs/document/assets/index.md.D0-LXlu-.lean.js

@@ -0,0 +1 @@
+import{_ as i,c as a,o as n,ak as l}from"./chunks/framework.xxfEszSJ.js";const g=JSON.parse('{"title":"安装使用","description":"","frontmatter":{},"headers":[],"relativePath":"index.md","filePath":"index.md","lastUpdated":1754013470000}'),p={name:"index.md"};function t(e,s,h,k,r,E){return n(),a("div",null,s[0]||(s[0]=[l("",50)]))}const c=i(p,[["render",t]]);export{g as __pageData,c as default};