deltas() function, closes #437

[LeaVerou]

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[facelessuser]

Shouldn't this have special handling for hues?

[svgeesus]

Shouldn't this have special handling for hues?

Yes, as I said earlier

[svgeesus]

Needs to calculate delta of the hue arc, not the angular delta

[LeaVerou]

I envisioned this as a low-level utility function, if users want to make this optimization for hue it's trivial to do so on the deltas returned.

That said, it should definitely constrain the ΔH returned in some way (possibly by also preserving the original). We shouldn't have a color with a hue of 350 and a color with a hue of 0 appear to have a ΔΗ of 350. It seems like this could follow shorter hue, possibly even take an argument for it.

[LeaVerou]

Ok, I’ve made several improvements:

• A hue interpolation setting, with "shorter" being the default.
• Fixed a bunch of issues around none handling, and added more tests.

[LeaVerou]

We could have another option for scaling the Δh by taking C/L into account, but not sure how that would work in a generic way.

[facelessuser]

Looks good to me. I would fix lint issues. related to the files in questions.

[facelessuser]

LGTM