Include exfat modules on zfsbootmenu

[nwildner]

As stated on the title, please include exfat module on zfsbootmenu, so we can mount it on emergency shells to copy files from external drivers.

While a lot of folks use FAT32 or NTFS for smaller external drivers, exFat is the only one that is recognized by all OSs (Windows, Linux, macOS, smart TVs, printers, etc) and I went into a situation where I had to copy the ZBM EFI recovery to my ESP and through the emergency shell I was not able to mount my external nvme which was exFat formated.

Please consider adding this module to ZBM :)