implement arch-release-promotion

[jelly]

{
  "developer": "David Runge <dvzrv@archlinux.org>",
  "files": [
    "file.gz.sig",
    "file.qcow2",
    "file.gz",
    "file.zst",
    "file.lkrn",
    "file.xz",
    "file.pxe",
    "file.efi",
    "file.iso"
  ],
  "name": "test",
  "pgp_public_key": "C7E7849466FE2358343588377258734B41C31549",
  "torrent_file": "test-2021.08.07.31065.torrent",
  "version": "2021.08.07.31065",
  "version_metrics": [
    {
      "description": "kernel version",
      "name": "linux",
      "version": "1.0.0"
    }
  ]
}

Read torrent data, md5sum, sha1 from disk.