Feature: Export useCharacterLimit

Hello 👋

I'm working on a custom text editor using Lexical and I highly appreciate the fact that you share so many plugins on the playground. I was wondering if it was possible to export `useCharacterLimit` from lexical so I can create a custom `CharacterLimitPlugin`. The output HTML doesn't match the one I want in my application so basically I'd like to create a custom one which uses `useCharacterLimit`

For now I copy / pasted the code from the hook into my project, but I believe it would be more convenient to directly import it from the lib.

Thanks 🙏