v1.9.0

This release updates FatFS (the FAT filesystem library) to R0.14b and updates
Monocypher to v3.1.2. Both updates were patch releases, but the FATFS update
changed the FAT serial number calculation so you may notice that those change.

• New features

  • Added the --metadata-key option to pull out single metadata values for
    convenience. E.g., fwup -m -i fwup.fw --metadata-key meta-uuid

• Bug fixes

  • Fixed an issue preventing filesystem encryption secrets from being passed
    via environment variables.