Add docs for pipectl transfer command

[khanhtc1202]

What this PR does:

As PR title

Why we need it:

Which issue(s) this PR fixes:

Fixes #6691

Does this PR introduce a user-facing change?:

• How are users affected by this change:
• Is this breaking change:
• How to migrate (if breaking change):

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 29.32%. Comparing base (5df1ef3) to head (da42103).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6768      +/-   ##
==========================================
- Coverage   29.33%   29.32%   -0.01%     
==========================================
  Files         598      598              
  Lines       63902    63902              
==========================================
- Hits        18744    18740       -4     
- Misses      43711    43714       +3     
- Partials     1447     1448       +1     

Flag	Coverage Δ
.	23.13% <ø> (ø)
.-pkg-app-pipedv1-plugin-analysis	32.43% <ø> (ø)
.-pkg-app-pipedv1-plugin-ecs	31.82% <ø> (ø)
.-pkg-app-pipedv1-plugin-kubernetes	58.37% <ø> (ø)
.-pkg-app-pipedv1-plugin-kubernetes_multicluster	61.89% <ø> (ø)
.-pkg-app-pipedv1-plugin-scriptrun	54.83% <ø> (ø)
.-pkg-app-pipedv1-plugin-terraform	37.95% <ø> (ø)
.-pkg-app-pipedv1-plugin-wait	33.04% <ø> (ø)
.-pkg-app-pipedv1-plugin-waitapproval	52.71% <ø> (ø)
.-pkg-plugin-sdk	50.14% <ø> (-0.20%)	⬇️
.-tool-actions-gh-release	19.23% <ø> (ø)
.-tool-actions-plan-preview	25.51% <ø> (ø)
.-tool-codegen-protoc-gen-auth	0.00% <ø> (ø)

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