[arch-releng] Pretty EFI splash

I think it would be cool to have the EFI splash screen show the same graphical image that the syslinux boot loader has. I played around a little to try to get it to work but failed. I used the systemd test as a basis for that [1]. Thoughts on pretty EFI boot loader? [1] https://github.com/systemd/systemd/blob/dd8352659c9428b196706d04399eec 106a8917ed/test/test-efi-create-disk.sh