ALl the ones except for build-image.nix are considered trivial. On the
latter, nixfmt makes some useful changes but by-and-large it is not
ready for that code yet.
Executes the previously added mdBook on the previously added book
source to yield a directory that can be served by Nixery on its index
page.
This is one of those 'I <3 Nix' things due to how easy it is to do.
