`gpgme-json` not in PATH while setting up for Mailvelope extension

[ajhalili2006]

@PlasmaPower

From that comment it sounds like that should be changed, but for now you might need to add gpgme.dev to your packages (or try it out with nix shell nixpkgs#gpgme.dev).

Thanks for the note since they are packaged separately unlike on most distros (library code + gpgme-* utility binaries), although I also caught that earlier. Going to update my NixOS/home-manager configurations soon.