without this, the code fence parser was getting thrown off if you didn't
have the pydot extension loaded, which was thwarting backwards
compatibility. this makes the pydot bits look like an attribute to the
vanilla parser, so at least then the vanilla markdown renders as
intended
this is server side, and a more standard format, and thus I like it more
than mermaid, which I've been using at work. but, I really wanted a
server-side option (see my manifesto) for drawing relationship graphs,
for D&D stuff of all things.
this adds an optional 'graphviz' feature to package installation which
consequently depends on pydot
