[meta] Documentation re-writting

[ArthurSens]

This is an meta issue, grouping all pages that we want to re-write.

Getting Started

• Introduction #82
• Getting Started becomes Installation Guide #83
• Compatibility stays as is.
• Rewrite design #84

Developer Guide

• PodMonitor page in Developer Guide #97
• [Developer Guide] Alerting routes #96
• ServiceMonitor page in Developer Guide #93
• PrometheusRule page in Developer Guide  #94
• Probe CRD page in Developer Guide #95

Platform Guide

• [Platform Guide] Writing a Getting Started page #101
  more to come

Community

to be discussed