Add a public documentation for the SD features

[sgmv]

We need to summarise and prepare public documentation for the SD.
URL: https://docs.otc.t-systems.com/status-dashboard/index.html

In the gitea repository, we have examples of how to do it.
Example:
https://gitea.eco.tsi-dev.otc-service.com/docs/status-dashboard/pulls/26/files

TODO:
Add section for info event: Incident / Maintenance Displays