Allow customization of tests color thresholds

[qmarcou]

Hi, I'm using your package within my CI workflow to avoid dependencies on external services and work on a private repo. I especially use the tests badge feature, but I find the color code misleading. I am personally not happy with even a single test failing, and to reflect this I'd like to have the displayed badge be orange or red for even a single test failed.

I could not find a way to change this in the docs and it seems the threshold values are currently hard coded: https://github.com/smarie/python-genbadge/blob/30b9121285a97cb96da44bb912cf865d1aec48fc/genbadge/utils_junit.py#L77-L91

Would you consider adding CLI arguments for this?

Anyway thanks for the package and work, Best