refactor(dpip): [PKG-DPIP-03] own windows and DOM resources in strict TypeScript

packages/artplayer-plugin-document-pip/README.md

@@ -6,6 +6,12 @@ Document PIP plugin for ArtPlayer
 
 [https://artplayer.org](https://artplayer.org/?libs=./uncompiled/artplayer-plugin-document-pip/index.js&example=document.pip)
 
+## Maintenance
+
+Source is split into strict TypeScript modules for window ownership, DOM migration,
+styles and controls. See [ARCHITECTURE.md](ARCHITECTURE.md) for lifecycle behavior,
+compatibility boundaries, tests and remaining native browser validation.
+
 ## License
 
 MIT © Harvey Zhao