chore: update READMEs and remove plugin-old

Author: nartc

libs/core/README.md

@@ -1,19 +1,19 @@
 # `angular-three`
 
-A custom Renderer for Angular 19+ that uses Three.js to render 3D scenes.
+A custom Renderer for Angular 20+ that uses Three.js to render 3D scenes.
 
 ## Documentation
 
 All public APIs are documented with JSDoc comments. Your IDE will provide inline documentation, parameter hints, and examples as you code.
 
 ### Official Documentation
 
-Please visit [angularthree-docs-next](https://angularthree-docs-next.netlify.app)
+Please visit [Angular Three Documentation](https://angularthree.netlify.app)
 
 ## Installation
 
 ```bash
-npm install -D angular-three-plugin@next
+npm install -D angular-three-plugin
 npx ng generate angular-three-plugin:init
 ```