Status Page documentation

What does this MR do?

Add documentation for Status Page as per #205499 (closed)

It covers the following sections:

• How to set-up
• Status Page layout
  • Incident detail page
• How it works
  • Publishing Incidents
  • Publishing updates
  • Adding comments
  • Changing the Incident status

Documentation on the list view is not done yet as that has not been implemented.

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Related to #205499 (closed)

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