Feature/add din99c and din99d

[rumpelrausch]

DRAFT

Features DIN99c and DIN99d. I'm unsure whether I understood all the internal culori concepts. It works, though.

Tests are still missing (WIP). Main problem: There are no publicly available examples for specific colors in DIN99c or DIN99d; We'd just have to trust the formula transcription was correct. The according deltaE tests should also be added.

If conversion back from these color spaces is really necessary someone else would have to do the math; That's beyond my capabilities.

GIT commit messages follow conventional commits.