Depend on `jupyterlite-core`

[jtpio]

The core functionality of the jupyterlite package is being extracted to a new jupyterlite-core package in https://github.com/jupyterlite/jupyterlite/pull/994.

This will allow site deployers to make slimmer deployments without having to bring the Pyodide kernel as well.

And let them use alternative kernels like Xeus Python only if they want to.

TODO

• [x] Try depending on jupyterlite-core built from https://github.com/jupyterlite/jupyterlite/pull/994
• [x] Update to the real jupyterlite-core dependency when a release is available (likely after https://github.com/jupyterlite/jupyterlite/pull/994 is merged)
• [x] Update the docs environment

[jtpio]

Keeping as a draft for now until jupyterlite-core is released.

[jtpio]

Alright looking good on the ReadTheDocs preview: https://xeus-python-kernel--114.org.readthedocs.build/en/114/

[jtpio]

Planning to make a new release with this change.

We could probably bump to 0.7.0 since the change of dependency might break some deployments? I guess some folks were maybe relying on jupyterlite to be installed automatically when installing jupyterlite-xeus-python.

[martinRenou]

Sounds good! Thanks