Add Lexical-based editor to payload's core

[AlessioGr]

Just leaving this here for documentation purposes, so you can also prioritize it in the roadmap if you do plan to invest time into it eventually.

Ref: https://github.com/AlessioGr/payload-plugin-lexical and #1443

[jakehopking]

I can't say I'm a big fan of slateJS, so I'll add my voice to this feature request 👍