`pip install -e` does not set up Jupyter extensions

[pkgw]

If you install pywwt in "editable" (developer) mode with pip install -e, the Jupyter components do not work because certain magic files do not get installed in that mode. Ideally, everything would work automagically; less ideally, we could tell people how to manually get things working in the mode; least ideally, we could tell people that this won't work and they need to install in non-editable mode if they want pywwt/Jupyter integration.

Files that don't get installed, I think:

etc/jupyter/jupyter_notebook_config.d/pywwt.json
etc/jupyter/nbconfig/notebook.d/pywwt.json
share/jupyter/lab/extensions/pywwt-X.Y.Z.tgz # ???
share/jupyter/nbextensions/pywwt/* # static files such as wwt.html