Get Tox Working

[rachelhsmith]

This PR addresses issue #37

The aim is to use tox to run tests across all variations of Django versions 2.2 - 4.0 and Python versions 3.8 - 3.10.

This PR will enable:

• tox to run locally by running 'tox' or 'poetry run tox'
• pytest to run locally on it's own by running 'pytest' or 'poetry run pytest'
• tox to run on pull requests
• Pytest to be used as the runner for tox

[jams2]

This is a great start, thanks!

This config only runs the tests against Python 3.10. It is running all of the tox envs, but against 3.10. Check the output of the setup-python action - we only install 3.10. These lines also tell us what Python we're running

The reason this is running all of the envs anyway is that the py$VERSION factors must be in the format pyNM for tox to recognise them as interpreter versions, not py-NM as we have here. https://tox.wiki/en/latest/user_guide.html#test-environments is the relevant section of the tox docs.

We need a matrix to run the tests once for each Python version.

The wagtail-localise config might be helpful. They use tox-gh-actions which we could consider. The relevant files are:

• tox.ini
• test.yml

[zerolab]

Drive-by review with a couple of notes/suggestions.
Feel free to ignore for a future PR

[jams2]

Could you also update the changelog please?