Moving away from relying on setuptools develop mode

[bmorris3]

Invoking setup.py is deprecated (you can catch up on what's preferred in this blog post, for example). Currently, jdaviz still uses the setuptools.setup function in develop mode to make symlinks for our custom voila template, named jdaviz-default. The template is defined in the source code here, and the linking on python setup.py develop is done here.

An improvement option to investigate:

• hatch is a python package manager that may cover our needs. Both voila (source) and Jupyter (source, blog) recently migrated to hatch, with the help of their hatch-jupyter-builder package.

Aside: @rosteen and I have found it helpful to find the available (=="installed"?) templates by running a script like this. Maybe we should offer a util like this to voila upstream?

:cat: