GetManifestAsync does not work with docker plugins

[rgl]

To install a docker plugin, one uses something like:

docker_plugin_reference="grafana/loki-docker-driver:2.2.1"
docker plugin install \
  --disable \
  --grant-all-permissions \
  --alias "$docker_plugin_reference" \
  "$docker_plugin_reference" \
    LOG_LEVEL=debug

And this is how the docker daemon contacts the docker hub registry and is able to download the image manifest:

And this is how this library GetManifestAsync does it but fails to download the image manifest:

The difference is, the docker daemon first manifest request uses a HEAD request to translate the manifest reference from the version 2.2.1 to the digest sha256:c7cf4544f8eee4e9d55e701e01f6ec5a290a807f0e75dfaf14ec463e3d973963 (which it obtained from the HEAD response docker-content-digest header), and only then, it uses a GET request to obtain the actual manifest.

I think this library should be changed to behave the same way.