add tests for the `color.nu` module (dragoon/komodo!121)

this also bumps Nushell to 0.93.0 to include the "extra" command `fmt`, see [Nushell 0.92.0](https://www.nushell.sh/blog/2024-04-02-nushell_0_92_0.html#incorporating-the-extra-feature-by-default-toc)