Test with dateutil timezones [Python, guided by maintainer]

[niccokunzmann]

At the moment, we check icalendar with zoneinfo and pytz.
We can also make sure that dateutil works.

• create a TimzoneProvider for dateutil
• parametrize the tests to work with dateutil (conftest.py)
• add possible additional tests

[c0d33ngr]

I'll work on this

[devdanzin]

We (@mtrd3v and I) are working on this.

[niccokunzmann]

@devdanzin @c0d33ngr @mtrd3v Thanks for taking this on! Please create a PR with some changes to indicate progress and work as soon as you have only a little bit done. Then, you can collaborate, review and inspire.
We can do many PRs and not everything has to be done perfectly in one go. You might also want to work on the same branch together. This is actually a big issue, so you will need each other for quality.

I do not lock issues or tell people they cannot contribute because someone else said that they would.
Happy coding and collaborating!

[mtrd3v]

I have created a PR.