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]

Codecov Report

❗ No coverage uploaded for pull request base (master@17a200f). Click here to learn what that means.
The diff coverage is n/a.

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Flag	Coverage Δ
#criv1alpha2_test	38.39% <ø> (?)
#integration_test_0	36.23% <ø> (?)
#integration_test_1	35.66% <ø> (?)
#integration_test_3	35.71% <ø> (?)
#node_e2e_test	34.17% <ø> (?)
#unittest	28.01% <ø> (?)

[allencloud]

LGTM