This is an initcpio hook that loads your root pool zfs password from a usb stick, as an alternative to modifying the zfs initcpio hook as mentioned in https://wiki.archlinux.org/title/Install_Arch_Linux_on_ZFS#Loading_password_from_USB-Stick.
This hook can also be used in ZFSBootMenu, meaning the same code and same usb can unlock your
root pool in ZFSBootMenu and Linux itself. This solution does not store your key in initramfs
.