Add packaging/freebsd/package.sh, matching the sibling craft apps. The release
workflow cross-compiles aarch64 FreeBSD in an x86_64 VM with CARGO_BUILD_TARGET
set; the script builds with --target, reads binaries from the target directory,
names the archive after the target arch, and checks ELF/FreeBSD/arch instead of
running binaries that cannot run on the host.
