Pre-render the graphs

[roberth]

It would be nice to have mdbook-mermaid invoke the renderer ahead of time. Some benefits

• Syntax errors can be caught early; during the site build process.
• Probably faster as inline SVGs are probably cheaper. Loading time comes mostly from having many files, and this way we can remove the two scripts.
• No complaints from readers who have disabled javascript.

I don't know if the mermaid does anything useful that's browser dependent, or whether that'd be important. If it is, the js could still be loaded I presume, but I really don't expect that to be needed.

[badboy]

You can use the mermaid cli to generate svgs or pngs. But I have currently no intention to build it into this tool. If you want though take the code, replace this part with an invocation of the CLI and insert a new image tag (and figure out where to put the image).

[roberth]

That's this part as a permalink for future reference.