Improve imports

[fcollonval]

Fix some imports and set jupyterlab-markup as dependency

I had to remove the auto disabling core factory. If it is set, the notebook editor is not available any more. I don't know why.

Sounds like a bug in JLab because if I manually set jupyter labextension disable "@jupyterlab/notebook-extension:factory", everything works fine.

[agoose77]

Thanks for cleaning these up, also needed to be done.

I'm not sure on the protocol for adding dependencies in the Python package, which is why I left it out until now. My gut instinct is that we should assume if the user is installing one extension via PyPI, they want both via PyPI, so I'm on board with the suggestion.

[agoose77]

Let's add an install for jupyterlab too so that we have jlpm. I'd still like to use a PEP517 builder with isolation for the package build stage.

[agoose77]

LGTM :)

[fcollonval]

Thanks I'm trying it on binder as I still have a doubt about the disabledExtensions setup in package.json. If it works, I'll then merge.

[fcollonval]

I confirm that if disabledExtensions is set, it breaks JupyterLab. So I remove it. I'll merge as the error is unrelated.