Update rcssmin to 1.2.1

[pyup-bot]

This PR updates rcssmin from 1.1.2 to 1.2.1.

Changelog

1.2.1

*) Change doc theme to "furo"

*) Remove build dependency pinning (resolves 18)

*) Update project boilerplate

1.2.0

*) Add support for nesting selector (&)

*) Update project boilerplate

1.1.3

*) Add support for Python 3.13

*) Update project boilerplate

Links

• PyPI: https://pypi.org/project/rcssmin
• Changelog: https://data.safetycli.com/changelogs/rcssmin/
• Homepage: https://opensource.perlig.de/rcssmin/