Roadmap v9

[zbeyens]

While we have a general roadmap, this is a discussion for what can come until next major release.

Core

• Use https://github.com/udecode/zustood for the store
• Replace hook actions with setter actions

Misc

• rename packages:
  • plate-x-ui to plate-ui-x then move them to the ui folder
  • plate-x-serializer to plate-serializer-x
• create @udecode/plate-headless package which contains all non-ui packages
• create @udecode/plate-ui package which contains all ui packages