Save version identifiers and/or Artwork in resulting MacOS pkg download

Description

It would be terrific to replicate what ipatool already does for iOS apps - it takes the passed-in Metadata from the download result payload and stores it in the archive, along with the artwork. It would be cool to see equivalent functionality when re-packaging (decrypting) the MacOS pkg, and would avoid the need to call list-versions on a MacOS app to find it out.