Thanks :) A great question. So, I believe Github simply built in support for Mermaid as just something they natively support. That means getting reladraw to "just work" in Github markdown files is sorta not possible. The workaround is rendering to SVG and linking to the SVG (obviously not nearly as convenient).

For tools like IntelliJ, VSCode, Obsidian, they would be easier to get working I think, as they all support plugins/extensions. That way, they'd know what to do when they encounter a fenced-in area starting with ```reladraw.