Move to the `jupyterlite` organization and mention in the documentation?

[jtpio]

Hey, thanks for putting this repo together!

Since some people might be interested in being able to embed JupyterLite in an mkdocs site, maybe it could be interesting to move this repo to https://github.com/jupyterlite and mention it somewhere in the docs, for visibility?

Even if the current state is still a draft or early version, we could still mark it as experimental for now.