Extend support for ARM in GNU Boot

Computers with ARM architecture are prevalent but GNU Boot currently doesn't support them. My focus has also shifted from the classic x86_64 laptops compatible with fully free BIOS to newer armv7 and beyond to armv8 computers. The defunct fully free Libreboot has supported a few Chromebooks that didn't require blobs to boot, thanks to efforts of contributors such as PaulK. I checked with him for basic guidance and I'm in need of a mentor from the GNU Boot project under the GNU umbrella (as GSoC 2026 approved organization). Having GNU Boot support ARM computers would play well into the efforts of fully free GNU/Linux-libre distributions such as Trisquel to complete freedom-respecting ARM laptops. My work will involve updating the previous code in Libreboot and (PaulK's fork libettereboot) for the Chromebook C201 and C100 laptops and porting GNU Boot to newer ARM targets found in coreboot. Since I'm a Embedded Systems Master's student, Google Summer of Code seems to be the perfect opportunity to extend the GNU Boot contributor team while providing basic funding for taking GNU Boot to the next architecture.