README: add docker run

[daixiang0]

What type of PR is this?

Uncomment only one /kind <> line, hit enter to put that in a new line, and remove leading whitespaces from that line:

/kind api-change
/kind bug
/kind cleanup
/kind design
/kind documentation
/kind failing-test
/kind feature
/kind flake

What this PR does / why we need it:

Use docker is a simple way to try KubeSpray.

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

[k8s-ci-robot]

Adding the "do-not-merge/release-note-label-needed" label because no release-note block was detected, please follow our release note process to remove it.

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[k8s-ci-robot]

Hi @daixiang0. Thanks for your PR.

I'm waiting for a kubernetes-sigs 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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Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: daixiang0
Once this PR has been reviewed and has the lgtm label, please assign vannten for approval. For more information see the Code Review Process.

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[yankay]

/ok-to-test

[daixiang0]

Do not get meaning about CI failure:

Using /builds/kargo-ci/kubernetes-sigs-kubespray/tests/ansible.cfg as config file
statically imported: /builds/kargo-ci/kubernetes-sigs-kubespray/roles/kubespray-defaults/tasks/no_proxy.yml
redirecting (type: callback) ansible.builtin.debug to ansible.posix.debug
ERROR! Invalid callback for stdout specified: debug