How to run a script on system shutdown/reboot

[Unstable Horse]

Good day, people. I am browsing the shepherd's info docs, and I can't
seem to find a way to run something right after either reboot, or halt
were invoked.

Something that is usually achieved by sticking a script into /etc/rc0.d
in classical init systems, or /usr/lib/systemd/system-shutdown in
systemd.

Can I somehow configure this from my system-wide config.scm? Or any way
at all, if that's not an option?

My particular use-case is unloading a faulty kernel module, that
prevents powering off the laptop right before shepherd actually tries
to shut it down.