[BUG] PyPI maintainer is off

[niccokunzmann]

Describe the bug

If you go to https://pypi.org/project/icalendar/ You can see that Betreuer: Christian Geier has the wrong email.

Expected behavior

All maintainers should be listed

This can be fixed in the pyproject.toml

Environment

• [ ] OS:
• [ ] Python version:
• [ ] icalendar version: 6.0.0

Additional context

• [ ] I tested it with the latest version pip3 install https://github.com/collective/icalendar.git
• [ ] I attached the ICS source file or there is no ICS source file

[niccokunzmann]

This is a problem of the build system.

Maintainer: Christian Geier
Maintainer-email: Nicco Kunzmann <niccokunzmann@rambler.ru>, Jaca <vitouejj@gmail.com>

What we do is correct: https://packaging.python.org/en/latest/guides/writing-pyproject-toml/#authors-maintainers

This is followed up here: https://github.com/pypa/hatch/issues/1747