Mermaid

More info in Mermaid.

graph TD; A-->B; A-->C; B-->D; C-->D; 
<div class="mermaid">
graph TD;
    A-->B;
    A-->C;
    B-->D;
    C-->D;
</div>
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
prevail! John-->>Alice: Great! John->>Bob: How about you? Bob-->>John: Jolly good! 
<div class="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!
</div>