Mermaidでシーケンス図を描く

例

```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!
```