`pullImageFromManifest` does not work without token URL

pullImageFromManifest does not work for registries not requiring authentication.

Example

nix expression:

devcontainer-base = nix2container.pullImageFromManifest {
      registryUrl = "mcr.microsoft.com";
      imageName = "devcontainers/base";
      arch = pkgs.go.GOARCH;
      imageManifest = ./devcontainer-base-manifest.json;
};

manifest:

{
  "schemaVersion": 2,
  "mediaType": "application/vnd.oci.image.manifest.v1+json",
  "config": {
    "mediaType": "application/vnd.oci.image.config.v1+json",
    "digest": "sha256:e1106c2b3c0c99ba03926a49daf44860944ba25a37058a6ef03a4a9542e1d660",
    "size": 8296
  },
  "layers": [
    {
      "mediaType": "application/vnd.oci.image.layer.v1.tar+gzip",
      "digest": "sha256:90e5e7d8b87a34877f61c2b86d053db1c4f440b9054cf49573e3be5d6a674a47",
      "size": 49582225
    },
    {
      "mediaType": "application/vnd.oci.image.layer.v1.tar+gzip",
      "digest": "sha256:27e1a8ca91d35598fbae8dee7f1c211f0f93cec529f6804a60e9301c53a604d0",
      "size": 24049172
    },
    {
      "mediaType": "application/vnd.oci.image.layer.v1.tar+gzip",
      "digest": "sha256:a19d29a2b395bc158cc522f5c504c327c116e7b7116c832f8f06020eccad6495",
      "size": 411
    },
    {
      "mediaType": "application/vnd.oci.image.layer.v1.tar+gzip",
      "digest": "sha256:141b387f51ce19730036f42286723694ff2e046c94804d0b91b8ca4f806133ee",
      "size": 134
    },
    {
      "mediaType": "application/vnd.oci.image.layer.v1.tar+gzip",
      "digest": "sha256:3f8e0f079df941f31884b19e3bb66637e7e064d38afc2c733b3e4edfa8a200f1",
      "size": 223
    },
    {
      "mediaType": "application/vnd.oci.image.layer.v1.tar+gzip",
      "digest": "sha256:c2d282ba72ab6ac0d192f5d5c88b0f948acb9df73d1facdc63faf582b7c0dc33",
      "size": 235
    },
    {
      "mediaType": "application/vnd.oci.image.layer.v1.tar+gzip",
      "digest": "sha256:7887253947105c355371a559ce01a0fe143d56246e308f674cc267ae2b5a6138",
      "size": 100075677
    },
    {
      "mediaType": "application/vnd.oci.image.layer.v1.tar+gzip",
      "digest": "sha256:a4e8e296b0549bbeb4ddf15d7463060cc571ae16ef65c7743065b8a0520be49d",
      "size": 166182953
    }
  ]
}

nlewo / nix2container

`pullImageFromManifest` does not work without token URL #104

Example