Docs: Add doc about kube-rbac-proxy

[camilamacedo86]

Feature Request

Is your feature request related to a problem? Please describe.
The new layout uses the https://github.com/brancz/kube-rbac-proxy to protect the project. SDK has not a doc that explains, what/when/why/how regards it.

Describe the solution you'd like
We need to add a section to better doc it and we might need first improve the docs in the upstream to just link it in our own.
The only kb doc that quotes it is : https://book.kubebuilder.io/reference/metrics.html

[asmacdo]

+1 improve this doc upstream and link to it

[openshift-bot]

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/lifecycle stale

[camilamacedo86]

/remove-lifecycle stale

[openshift-bot]

Issues go stale after 90d of inactivity.

Mark the issue as fresh by commenting /remove-lifecycle stale.
Stale issues rot after an additional 30d of inactivity and eventually close.
Exclude this issue from closing by commenting /lifecycle frozen.

If this issue is safe to close now please do so with /close.

/lifecycle stale

[camilamacedo86]

/lifecycle frozen

[sathieu]

Maybe kube-rbac-proxy usage should be removed?

Ref: kubernetes-sigs/kubebuilder#3907 (by @camilamacedo86 😉 )