KEP-3104: Add kubectl kuberc command section

[ardaguclu]

• One-line PR description: Add kubectl kuberc command to generate kuberc files.

• Issue link:

  • Discussion link
  • Separate kubectl user preferences from cluster configs #3104

• Other comments:

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ardaguclu

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[ardaguclu]

/hold
for PRR review

[ardaguclu]

for sig-cli
/cc @soltysh
for PRR
/cc @johnbelamaric

[ardaguclu]

I think, we can also consider kubectl pref or kubectl preference, etc.