Add support for Pop!_OS

[ZeTriUm]

[aguslr]

It seems that the latest version of Pop! OS no longer uses loopback.cfg so this won't work. I've tried the usual configuration for Ubuntu, but it hangs while looking for the CD:

for isofile in $isopath/pop-os*.iso; do
  if [ -e "$isofile" ]; then
    regexp --set=isoname "$isopath/(.*)" "$isofile"
    submenu "$isoname ->" "$isofile" {
      iso_path="$2"
      loopback loop "$iso_path"
      menuentry "Try or Install Pop_OS" {
        bootoptions="iso-scan/filename=$iso_path boot=casper hostname=pop-os username=pop-os noprompt ---"
        linux (loop)/casper/vmlinuz.efi $bootoptions
        initrd (loop)/casper/initrd.gz
      }
    }
  fi
done

[queeup]

~~Is there a way to boot POP atm?~~ : https://github.com/pop-os/iso/issues/243