docs: auto generate pouch cli/api/contributors docs via code

[pouchrobot]

Signed-off-by: pouchrobot pouch-dev@alibaba-inc.com

1.Describe what this PR did This PR is automatically done by AI-based collaborating robot. Pouchrobot will auto-generate cli/api document via https://github.com/spf13/cobra/tree/master/doc every day.

2.Does this pull request fix one issue? None

3.Describe how you did it We use the following user input CLI document generating command in pouchrobot to generate CLI doc: go build -o /usr/bin/pouch ./cli; pouch gen-doc

For API part, we use a tool swagger2markup to make it.

4.Describe how to verify it None

5.Special notes for reviews The cli/api doc must be automatically generated.

[codecov[bot]]

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[fuweid]

duplicated with #2996