feat(pkgctl): add json output to version check command

Closes #237 (closed)

Example json output:

[
  {
    "pkgbase": "_test",
    "status": "failure",
    "message": "no PKGBUILD found",
    "local_version": null,
    "upstream_version": null,
    "out_of_date": null,
  },
  {
    "pkgbase": "ruby-grpc",
    "status": "failure",
    "message": "configuration file not found: .nvchecker.toml",
    "local_version": "1.67.0",
    "upstream_version": null,
    "out_of_date": null,
  },
  {
    "pkgbase": "asciidoctor",
    "status": "warning",
    "message": "local version is newer than upstream",
    "local_version": "2.0.23",
    "upstream_version": "2.0.22",
    "out_of_date": false,
  },
  {
    "pkgbase": "xmms2",
    "status": "success",
    "message": null,
    "local_version": "1.9.4",
    "upstream_version": "0.9.4",
    "out_of_date": false,
  },
  {
    "pkgbase": "vcspull",
    "status": "success",
    "message": null,
    "local_version": "1.31.0",
    "upstream_version": "1.32.0",
    "out_of_date": true,
  }
]