feat(contrib): add /boot/{a,b}.nsh scripts on Arch
feat(contrib): add /boot/{a,b}.nsh scripts on Arch

Based on:

    https://wiki.archlinux.org/title/EFISTUB

if my boot entries get blown away (eg. by a BIOS update), I should be
able to boot from the installation medium, get into a UEFI shell, and
run something like:

    FS1:
    a

to boot off the drive, after which I can do the steps described in
"Applying BIOS updates" in:

    https://wincent.com/wiki/Arch_Linux_cheatsheet

a little more easily (ie. via copy-paste).

I might also consider dumping the efibootmgr commands themselves into a
script to make running them easier...

wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent