Mermaid diagrams Pt 1

Seems @manulera came up with https://github.com/manulera/ontology_viewer which looks like its doing a subset of obographviz, outputting pretty github embeddable mermaid graphics:

https://github.com/pombase/fypo/issues/4166#issue-1275033122

@manulera obographviz is the tool we generally use for making the graphic of the kind you made on the issue above. @cmungall @manulera is the new PomBase curator!

Start with the linked ontology_viewer project and the referenced FYPO issue to understand the proposed Mermaid output and how it relates to obographviz. Clarify the intended Mermaid subset and acceptance examples before implementation; done means the requested GitHub-embeddable diagrams are produced.

Written by the indexing model from the issue text.