hex files in release

Hello world :-) I just encountered a situation where I need to put both Bootloader and Interface firmware into a bricked interface. Providing `hex` files with a release would make my life a lot easier because write address would be included right inside that `hex` file. I guess `hex` could also be used to flash Bootloader and Interface via UMS, right?

Start by examining the release process and the Bootloader and Interface firmware artifacts. Determine how release images are produced and whether HEX files preserve the required write addresses for UMS flashing; done means both requested firmware images are available as usable HEX files in a release.

Written by the indexing model from the issue text.