Changing Python requirements

[hubman-star]

Change the minimum required Python version since the package "pillow" cut the Python 3.8 support, working only on Python 3.9+.

https://pypi.org/project/pillow/#files

[hubman-star]

Probably because of Python 3.8 EOL, and last version to work on Windows Vista and Windows 7

[RaduTek]

Hi, the Readme file is wildly out of sync with the current code on the main branch. I didn't get around to updating it.

In pyproject.toml I've set the minimum Python version to 3.13, as I'm developing and testing with it, and I've also used some language features introduced in 3.13.

Thanks for the report though, I'll keep this open until I update the Readme file. The command line interface has also changed slightly so that needs Readme updates too :)