Mermaid - sequence diagram

Syntax

{{#mermaid:sequenceDiagram
 participant Alice
 participant Bob
  Alice->John: Hello John, how are you?
  loop Healthcheck
   John->John: Fight against hypochondria
  end
  Note right of John: Rational thoughts <br/>prevail...
   John-->Alice: Great!
   John->Bob: How about you?
   Bob-->John: Jolly good!
}}