In code blocked fenced messages support mermaidjs charts in addition to other syntax highlighting

In messages you are able create code blocks that are language aware, like:
```csharp
var a = “my string”;
```
It would be super cool to support mermaidjs (https://mermaid.js.org/) charts and graphs in messages as well!

Something like this:
```mermaid
flowchart TD
    Start --> Stop
```
And have that text rendered as a chart!