Support Embedded Mermaid.js Diagrams in CodeTour-Flavored Markdown

[Nezteb]

I find diagrams often go well docs, and it'd be neat if CodeTour supported embedded Mermaid.js diagrams like GitHub does:

flowchart LR
    A[Hard edge] -->|Link text| B(Round edge)
    B --> C{Decision}
    C -->|One| D[Result one]
    C -->|Two| E[Result two]

The above looks like this when formatted as regular Markdown:

flowchart LR
    A[Hard edge] -->|Link text| B(Round edge)
    B --> C{Decision}
    C -->|One| D[Result one]
    C -->|Two| E[Result two]

Links:

• CodeTour-Flavored Markdown Reference
• Mermaid.js Docs
• GitHub's Mermaid.js Docs
• Extension: Markdown Preview Mermaid Support