15: color theme generation (#17)

* add a script to automatically compute color gradients

* add the possibility to compute complitely random colors

* add tests for the random color generation

* create a whole palette and not just a gradient

* refactor into functions and add doc or TODOs

* move the theme generation to function and add light switch

* add a flag to get only the gradient

* add a simple default theme generation

* add missing documentation

* add some level of effect with the light switch

* make all the colors in the theme real arrays

* add some deterministic transformations

* remove the clipping on the hue

Clipping the saturation and the brightness between 0 and 1 does
make sense as these values only leave on that segment. However, the
hue value lies on a clock, i.e. 1 wraps back to 0. Thus the script
should not clip the hue, otherwise everything tends to turn red
when applying a big bias.

* add the flags to control the theme generation

* put the base colors in the same structure

* add a function to pick the ground colors

* add random variations controlled by temperature

* refactor the script with black

* make sure -h mentions False, not false or 'False'

Co-authored-by: a2n-s <[email protected]>