👌 Refresh template plugin

[chrisjsewell]

• Move to flit for PEP 621 compliant build (see also https://github.com/aiidateam/aiida-core/pull/5312)
• Remove setup.py,setup.json, MANIFEST.in, check_version.py, and .coveragerc
• Set requires-python = ">=3.7"
• Move from yapf to black for code formatting
• Add isort and pyupgrade pre-commit hooks
• Move documentation theme from sphinx-rtd-theme to furo
• Add tox configuration (in pyproject.toml)

Note the setuptools reentry_register hook is no longer possible, although reentry is anyway removed in AiiDA v2 (and I never found this to actually work?).

[chrisjsewell]

Why furo?

It's by me good friend and maintainer of pip; among others their documentation uses it: https://pip.pypa.io It just looks great. I'm literally looking to see if I can create an extended theme out of it, with the extra bells and whistles that sphinx-book-theme has (like the issue buttons)

Indeed - e.g. this would anyhow not work when the package was distributed as a wheel

Yeh, FYI I see why lots of the packages on aiida-registry didn't include a wheel lol: because the command in publish-on-pypi.yml here was python ./setup.py sdist 😬