Scuttle should be able to render Markdown with embedded Mermaid codeblocks

[rogeruiz]

While working on the Threat Modeling Guide, @commit-dkp found a limitation in the way Scuttle renders diagrams. It would be nice to have Scuttle render codeblocks in *.md file which would allow for Mermaid and Markdown syntax to be displayed on the same page for Threat Modeling diagrams.