Proposal for new keys to promote multi-booting

[Splayer0]

Multi-Booting ISO from a USB has always been a challenge for users. Tools like Ventoy solve this by using hard-coded config options for each distribution which makes it cumbersome. I have deduced that a new key extending the existing UAPI.1 Bootloader specification will be able to solve the issue. This new key will contain the path to the iso file to be used to find the kernel and initrd. Additionally another called iso_type may also be introduced which define the initramfs framework (dracut, Casper etc). I believe that this will simplify the process for multi-boot iso and effectively remove the need for hard-coded configs for each distro which is done by tools like Ventoy.