Add a discussion on perceptual uniformity

[PaulJWright]

For many applications, a perceptually uniform colormap is the best choice. There should be a section describing what this is and providing examples on perceptually uniform (sequential) colour tables. These are frequently found in python, e.g. plasma, magma, etc. (https://matplotlib.org/tutorials/colors/colormaps.html)

Other references:

https://colorcet.holoviz.org/