Getting Started becomes Installation Guide

[ArthurSens]

• Rename "Quick-Start" to "Installing Prometheus-Operator"
• This page will focus on installation only, accessing different tools or making modifications will be handled in Developer/Platform guide.
• Here we will provide an "easy" installation guide for the Operator. Full permissions, no RBAC explanation, step-by-step follow through and everything will work (Complex RBAC permissions can be explained in the platform guide).

Format can follow https://keda.sh/docs/2.14/deploy/#yaml

Anchors at the top with all different methods, user clicks on the preferred method and will be redirected to the related part of the page.

At the bottom, we ask user to double-check the compatibility page, to make sure they installation follows what we expect.

[ArthurSens]

Solved by #87 and prometheus-operator/kube-prometheus#2455