Improve palette generation

[FiratUsta]

Currently the palette generation is good enough for my intended usage, which is creating color palettes for digital art. However, the created palettes are not great for design purposes.

Palette generation could be improved by ensuring that the generated palettes cover all necessary colors for legibility (ie. a background, a foreground and an accent color) and that these colors abide by certain standards (ie. dark/light mode options, abiding color contrast standards for accessibility etc.)

[FiratUsta]

Moving this to 3.x release because this would be a breaking change (will break existing URLs and codes from version 2)