Jupyterlab 3 support

It looks like the current version of jupyterlab-prodigy doesn't yet support Jupyterlab 3. Are there plans to update it?

ValueError: The extension "jupyterlab-prodigy" does not yet support the current version of JupyterLab.

Ah, I think I missed the stable v3 announcement for JupyterLab. But yes, we definitely want to support the new version and I hope there's not too much that needs to be changed. I'll put in on our list of enhancements :slightly_smiling_face:

(Btw, the extension code is here so if there's anything obvious that needs to be updated, feel free to submit a PR: GitHub - explosion/jupyterlab-prodigy: 🧬 A JupyterLab extension for annotating data with Prodigy)