Please Support PlantUML and D2

# Feature request

## Summary

PlantUML is an open source project for Diagram-as-code. It can generate popular UML diagrams by coding. D2 is a similar project.

https://plantuml.com/sequence-diagram
https://d2lang.com/tour/sequence-diagrams/

## Examples

**PlantUML Sequence Diagram**
```puml
@startuml
participant User

User -> A: DoWork
activate A

A -> B: << createRequest >>
activate B

B -> C: DoWork
activate C
C --> B: WorkDone
destroy C

B --> A: RequestCreated
deactivate B

A -> User: Done
deactivate A

@enduml
```


**D2 Sequence Diagram**
```d2
shape: sequence_diagram
alice -> bob
bob."In the eyes of my dog, I'm a man."
# Notes can go into groups, too
important insight: {
bob."Cold hands, no gloves."
}
bob -> alice: Chocolate chip.
```


先阅读 issue 中链接的 README 愿景，然后查看 PlantUML 和 D2 示例及其文档。定义对于 DevDocs 而言“支持”意味着什么，以及两种格式的成功渲染或集成应当是什么样的；该 issue 未指定实现文件或测试。

由索引模型根据 Issue 内容生成。