[DOC] Integrated Alerting Usage documentation

the goal: describe IA  UI and the idea behind the feature

See  the parent Epic (  ) for linked documents 

•  The feature will be in Tech preview, but visible for the user 

  • no need to "hide" the Documentation but a clear statement of its Tech preview is needed. Inclide  into the menu section 

• Description of the UI

  • Communication Settings

  • Feature toggle in Advanced settings 

  •  IA usage  in general

• What is IA, concept  , etc 

• Architecture update