Adding ram only, shared func for init, ubuntu version as variable and secure boot

live_exam_os/.env.example

live_exam_os/Dockerfile

live_exam_os/Makefile

live_exam_os/README.md

live_exam_os/build.sh

live_exam_os/config/00-bootloader/grub.cfg

live_exam_os/config/00-bootloader/grub.efi.cfg

live_exam_os/config/00-bootloader/limine.conf

live_exam_os/config/00-bootloader/limine_casper.conf

live_exam_os/config/00-bootloader/limine_pxe.conf

live_exam_os/config/01-packages_install/packages

...-customisation/etc/NetworkManager/NetworkManager.conf.bak

...ation/etc/NetworkManager/conf.d/10-default-wired.conf.bak

...g/02-customisation/etc/NetworkManager/conf.d/dns.conf.bak

live_exam_os/config/02-customisation/etc/challenge

live_exam_os/config/02-customisation/etc/default/keyboard

...s/config/02-customisation/etc/initramfs-tools/hooks/nexus

..._os/config/02-customisation/etc/initramfs-tools/hooks/pxe

.../config/02-customisation/etc/initramfs-tools/scripts/init

...config/02-customisation/etc/initramfs-tools/scripts/nexus