That project is just Claude run rampant. Actually attempt to read this:

https://github.com/Latias94/merman/tree/83e3ea74bf4da30089a8...

Very nice, bookmarked. I built something similar as an Astro plugin using svgdom: https://better-static-sites.github.io/build-tools/mermaid/

It still boggles my mind that mermaid's devs think you need an entire freakin' browser to render an SVG. Sometimes I think people need to be reminded of the fundamentals.