JCh interpolation

[NateBaldwinDesign]

It would be nice to have JCh interpolation available for creating color maps. This is a nicer method of interpolation when you want to have a smoother transition across chroma from one color to the next.

This is similar to Lab/Lch interpolation outputs. Here is a comparison of interpolation in Jab vs Lab vs Lch from a blue to green color:

When visualizing this interpolation difference between cartesian and polar adaptations of color space, the polar takes a more curved transition. This can sometimes yield more aesthetically balanced color maps. Here is a visualization from top-down in LAB color space for the same scales (interpolated to black and white as well).

Lab interpolation in Lab space is purely linear, whereas Lch interpolation in Lab has curvature. This same curvature from a JCh interpolation would be desirable to include in this d3-cam02 library.