PlantUML Diagrams

If you have PlantUML installed and available on your path, mkbook will try to render any code blocks with a language tag of plantuml as inline SVG images.

For example:

```plantuml
@startuml
Alice -> Bob: Authentication Request
Bob --> Alice: Authentication Response

Alice -> Bob: Another authentication Request
Alice <-- Bob: Another authentication Response
@enduml
```

is rendered as:

AliceAliceBobBobAuthentication RequestAuthentication ResponseAnother authentication RequestAnother authentication Response

This feature is still experimental, but I find it handy for my books.

Next chapter: “KaTeX (Math) Formulas”