Feature Request: Mermaid support

[drbh]

Hi, it would we awesome to have mermaid support. I'm not sure if this would be helpful to others but I can look into adding support in the future (unless someone else is working on this sooner)

[tengomucho]

Just to give a background: it allows to add a scheme described in text, easier to maintain. I added on eon Tgi and I'd love to see it rendered as in github!