Add Docker Hub authentication example

[laupow]

Document how to configure containerd to authenticate to a Docker Hub registry.

Resolves #8612

[k8s-ci-robot]

Hi @laupow. Thanks for your PR.

I'm waiting for a containerd member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

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[mikebrow]

thanks for your example, see comment.. can you normalize the formatting with the other example pls :-)

[mikebrow]

you might need to rebase to pick up the latest ci/cd fixes.. cheers

[mikebrow]

LGTM
noting that this example is also deprecated until a suitable replacement design is provided, see enclosing section..

[alexeyatbluescape]

This is great, but still not clear enough. We should be creating file /etc/containerd/certs.d/docker.io/hosts.toml, without that file this does not work (at least in EKS 1.26)

reference: #8612

I would suggest adding

mkdir -p /etc/containerd/certs.d/docker.io
cat << EOF > /etc/containerd/certs.d/docker.io/hosts.toml
server = "https://docker.io"

[host."https://registry-1.docker.io"]
  capabilities = ["pull", "resolve"]
EOF

this command somewhere in the readme.