Update extension to work with jupyterlab 3.0

[parente]

Highlights

• Frontend and server-side extensions included in a single pip installable package
• Frontend extension is compiled at packaging time, not at install time
• Rebase release mechanics on the latest recommandation in https://github.com/jupyterlab/extension-cookiecutter-ts
• GitHub Action to lint, build, check install, package, and check package install

Some of the work put into this PR is visible at https://www.twitch.tv/videos/855634128 for the next week or so at least. The README has the new install and developer setup instructions.

[riderx]

Hey @parente i'm ussing your plugin in jupyter 3 and it seem to work only without jupyterhub
If you clone https://github.com/jupyter-naas/naas
and do ./install -r you will see your search working but not in binder our binder:
https://mybinder.org/v2/gh/jupyter-naas/naas/main?urlpath=lab
I saw your binder work but I have no clue why not our :/
If you have time to check !