Delete old code

[JiuqingSong]

I have copied all v8 packages into a new branch roosterjsv8.

So now we can delete all v8 packages. This change includes:

1. Delete v8 packages
   • roosterjs-editor-types
   • roosterjs-editor-types-compatible
   • roosterjs-editor-dom
   • roosterjs-editor-core
   • roosterjs-editor-api
   • roosterjs-editor-plugins
   • roosterjs-react (Later we can create v9 package for react wrapper)
2. Delete old demo site
3. Fix build scripts
4. Copy the build result of legacy demo site to assets folder, and change the link in new demo site to point to this file
5. Copy the build result of legacy doc zip file, and add link
6. Update readme files

Remaining work:

• Port roosterjs-react to roosterjs v9
• Use roosterjs-react@9.x from demo site