This is an example repository which shows off the action Compile Mermaid Markdown (Marketplace).

Generation of diagrams and flowcharts from text in a similar manner as markdown. Ever wanted to simplify documentation and avoid heavy tools like Visio when explaining your code? This is why mermaid was born, a simple markdown-like script language for generating charts from text via javascript. (website)

Mermaid markdown is not natively handled by github markdown parsing (see gitlab). But there is value in graphs to represent non-tabular data! This enables a repo to focus on the markdown content without having to worry about setting up the toolchain to compile mermaid markdown to an image