Add rendering of Mermaid diagrams

[FerLuisxd]

Mermaid allow the rendering of diagrams from markdown-like text snippets. Code-highlighting could be reused to render them when setting mermaid as the languaje.

[FerLuisxd]

#533

[walterrowe]

+11 for this feature

This is an important feature!

Graph LR

ClassDef red fill:#e33,color:#3ee,stroke:#3ee,stroke-width:2px;
ClassDef grn fill:#3e3,color:#e3e,stroke:#e3e,stroke-width:2px;
ClassDef blu fill:#33e,color:#ee3,stroke:#ee3,stroke-width:2px;

style box fill:#3e3,color:#e3e,stroke:#e3e,stroke-width:2px;

Subgraph box[My Box]
A:::red --> B:::grn --> C:::blu
End

linkstyle 0 fill:#e33,color:#3ee,stroke:#3ee,stroke-width:2px;
linkstyle 1 fill:#3e3,color:#e3e,stroke:#e3e,stroke-width:2px;

[matheusmacedoap]

Seria um ótimo recurso!!!

[Fa7C0n]

related -> https://github.com/github/markup/issues/533