mermaid graphs are not rendering

[balhoff]

Nice mermaid figures in here:

https://github.com/OBOAcademy/obook/blob/master/docs/explanation/taxon-constraints-explainer.md

Come out as source code in here:

https://oboacademy.github.io/obook/explanation/taxon-constraints-explainer/

[matentzn]

@souzadevinicius can you fix this? You know how it's done! Thanks!

[balhoff]

@sujaypatil96 pointed out to me that there is a plugin for this: https://github.com/fralau/mkdocs-mermaid2-plugin

He also mentioned this example to require the plugin: https://github.com/microbiomedata/nmdc-schema/blob/main/mkdocs.yml#L7

[matentzn]

Yes we are using it on pheval