Using built-in modus themes

[Tor Kringeland]

I'm trying to configure and use the modus themes as described in [1].
I'm on a build of Emacs 29 so these are built in.  While I can enable
the themes by using `load-theme', if I execute

  (require 'modus-themes)

as described in [1] I get an error saying that the file is missing.
However if I first load a theme using `load-theme', then executing the
above yields no error.

Shouldn't running the above work since the themes are part of Emacs now
(so that I could put it in my config)?  I'm running `emacs -Q' and this
fails then.


- [1] https://gitlab.com/protesilaos/modus-themes