Generate terminal color schemes.

Xiwal is a tool that generates color schemes from colors. The colors can either be specified directly or extracted from an image.

It is massively inspired by pywal, but it also has some important differences:

• Xiwal focusses on terminal color schemes. There is no integration with gtk, i3, polybar, etc.
• The colors are reordered to match the traditional "red, green, yellow, blue, purple, cyan" structure as close as possible.
• All generated color schemes use the same CIE Lab lightness levels. They are based on my personal experience/taste.
• Since red and green are important signal colors (e.g. in diffs), their saturation is increased.