Github supports mermaid, just use this syntax:
We can create diagram: flowchart, sequence diagram, class diagram, ….
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!
Mermaid helps us to generate diagram: