Feature request: Add an override for `shadow`

[Walheimat]

Hello. First of all: thanks for the theme, it's very nice.

One minor issue I have is that some of the standard faces aren't overridden, most notably shadow (see faces.el line 2411 and up in Emacs 29).

If you don't have time I could have a look as well. But I'm not sure how you feel about adding additional colors because at first glance none of the defined once would be a great match.

[nickav]

thanks, glad you like it! maybe if there was one consistent shadow color to use for all shadows that could work?

i am not actively maintaining this but am happy to merge any PRs