howto-fix-boot-manjaro.md

if ~ error: file `/boot/vmlinuz-5.13-x86_64' not found.

1. https://forum.manjaro.org/t/howto-recovering-from-an-interrupted-update-upgrade/132762
2. still on terminal, after mount with the command manjaro-chroot -a:

set -e
exec grub-mkconfig -o /boot/grub/grub.cfg "$@"
mkinitcpio -P```