Sub-package to hold data (fonts) for mplhep.

Fonts distributed in this package have open licenses and can be redistributed. While it would be preferable to download the files from their original repositories, there is no convenient way to do that due to varying repo structures. The following fonts are included:

https://ctan.org/pkg/tex-gyre-heros

https://ctan.org/pkg/tex-gyre-termes

https://github.com/mozilla/Fira

https://github.com/firamath/firamath