Add more diagramming tools

Author: pengqun

README.md

@@ -338,6 +338,11 @@ One diagram is usually worth more than a thousand words.
 
 - [Excalidraw](https://github.com/excalidraw/excalidraw) - An open source virtual hand-drawn style whiteboard for sketching hand-drawn like diagrams.
 - [draw.io](https://github.com/jgraph/drawio) (Open Source) - A JavaScript, client-side editor for general diagramming.
+- [Mermaid](https://github.com/mermaid-js/mermaid) - A diagramming and charting tool that renders Markdown-inspired text definitions to create charts.
+  - [Mermaid Live Editor](https://mermaid-js.github.io/mermaid-live-editor/) - A live editor for Mermaid diagrams.
+- [PlantUML](https://github.com/plantuml/plantuml) - Allows users to create diagrams using a simple syntax.
+- [Lucidchart](https://www.lucidchart.com/) - Generate visuals automatically with AI and data imports, or build your own using intuitive diagramming tools.
+- [OmniGraffle](https://www.omnigroup.com/omnigraffle/) - A Mac-only diagramming tool that offers a wide range of features for creating diagrams.
 - [(Chinese) Architecture Diagramming: Tools and Methodologies](https://developer.aliyun.com/article/774446) - It discusses the benefits of using diagrams in architecture document, and highlights some standards and best practices.
 
 ### Multimedia