Contentrules.slack

- Nothing changed yet.

- Use `requests` instead of `httpx`, as the former is already distributed with Plone.
[ericof]

- Update Sphinx theme used in the documentation
[ericof]

- Use [`pytest_plone`](https://pypi.org/project/pytest-plone/)
[ericof]

- Deploy documentation to https://collective.github.io/contentrules.slack
[ericof]

- Use `pytest` instead of `unittest`
[ericof]

- Drop dependency on `ftw.slacker`
[ericof]

- Drop support to Plone 5.2
[ericof]

- Support to Plone 6.0, Python 3.8 to 2.11
[ericof]

- Update documentation
[ericof]

- Fix "TypeError: expected string or bytes-like object" when one attribute of action is not set.
[ericof]

- Add Plone 5.2 / Python 3 support.
[ericof]

- Drop Python 2.7 support.
[ericof]