Update packaging to use more modern python practices

[jasongrout]

This updates the cookiecutter to use setup.cfg, etc. See https://setuptools.readthedocs.io/en/latest/build_meta.html

To generate a wheel, I think recommended practice to now use python -m build, for example.

• Add install.json for the jlab extension
• Error: warning package.json: No license field

[jasongrout]

CC @ibdafna

[jasongrout]

python -m build doesn't currently work because yarn cannot find jupyter labextension build - perhaps somehow a consequence of the virtual env the build process sets up? python -m build --no-isolation does work if the build dependencies are installed.

Also, it's unfortunate that the pyproject.toml cannot say that nodejs or yarn are required :(. I realize this is a complication from us building a package that spans two packaging ecosystems, of course.

[jasongrout]

python -m build doesn't currently work because yarn cannot find jupyter labextension build - perhaps somehow a consequence of the virtual env the build process sets up? python -m build --no-isolation does work if the build dependencies are installed.

This is because of this bug in build: pypa/build#214

So this PR is stalled until at least that bug is fixed and released.

[vidartf]

That bug was fixed and released yesterday 🚀