Upgrade to JupyterLab 4.0.0 beta

[fcollonval]

• [x] Add integration tests
• [x] Add new package mathjax2
• [x] Check binder
• [x] Cross compatible JLab 3 / 4

[github-actions[bot]]

:point_left: Launch a Binder on branch jupyterlab/jupyter-renderers/maintenance/jupyterlab4