Split out server/public rooms and retro into separate plugins

[bollwyvl]

References

• fixes Make lab extension work without (full) server extension #25

Changes

• separates the server/public room provider from the core plugin
  • can be independently disabled via disabledExtensions or the jupyter labextension disable CLI
• adds more commands
• adds basic/hacky support for retrolab (Quick access to creating a seperate browser tab which only comprises of the video chat #44) as a separate plugin
• add JVC-PUBLIC route
• adds some skeleton jupyterlite config docs

Follow-on Work

• add a JupyterLite docs site with videochat enabled
  • may be necessary to kick the tires, fully, vs e.g. jupyterlab 3.1.0rc0+

[bollwyvl]

Linger perms issues, but here's docs:
https://jupyter-videochat--38.org.readthedocs.build/en/38/