Check CMC (l:c) formula for correctness

[danburzo]

The CMC color difference function performs the worst in this comparison:
https://beta.observablehq.com/@danburzo/nearest-css-named-colors

This makes me suspicious there's an error somewhere in the implementation.

[danburzo]

Also, HSL Euclidean distance is similarly suspect here

https://beta.observablehq.com/@danburzo/nearest-color

[danburzo]

For HSL — and, for that matter, all spaces that contain a hue element — the Hue will have an inordinate impact, since it's in the range [0, 360), while the other components are in the range [0,1]. We also need a way to perform hueDistance (shortest path) rather than normal distance between them.