simp1e: add module

[boomshroom]

Simp1e Cursors allow for generating cursor themes with a given color scheme. This patch enables generating a Simp1e cursor theme based on the global base16 theme. It will also automatically set said cursor theme as the stylix-global cursor theme if enabled. As most users likely have their own choice of cursor theme, it is not enabled by default.

Currently, it deletes all prior color schemes in order to speed up building. As it automatically sets the theme name, this shouldn't be an issue.

I don't know how efficient generating the color scheme with pkgs.writeText is compared to writing the file directly in the build, but I'm not quite comfortable enough with Bash to be confident it'd be done properly, so instead it simply copies from the generated derivation.