Nox integration

[johnthagen]

A possible replacement for tox is nox: https://nox.thea.codes/en/stable/

Related to #16, consider nox-poetry: https://github.com/cjolowicz/nox-poetry

As small side effect of this is that flake8 configuration would need to move back into flake8.ini or setup.cfg until #29 is complete.

[johnthagen]

For GitHub Actions integration, consider: https://github.com/marketplace/actions/setup-nox

It is also referenced in the main nox repo: https://github.com/wntrblm/nox/blob/main/docs/tutorial.rst#installation

[johnthagen]

Supporting Poetry 1.2 dependency groups would greatly clean up dependency declaration and usage compare to the current pip-tools/tox side of things.

• Support installing Poetry dependency groups cjolowicz/nox-poetry#663

It also seems as though the creator of nox-poetry might deprecate nox-poetry when Poetry 1.2 launches, however.

• Poetry dependency groups cjolowicz/nox-poetry#481 (comment)

[johnthagen]

PyCharm does not currently have Nox-specific support: https://youtrack.jetbrains.com/issue/PY-37302