feat(markdownPreview): integrate ZenUML diagrams support

[yufeikang]

Title: Add Support for ZenUML Diagrams in Markdown Preview

Description:

This pull request introduces a new feature that integrates ZenUML diagram rendering into our Markdown preview functionality. By leveraging the @mermaid-js/mermaid-zenuml package, users can now include ZenUML diagrams directly within their Markdown files, enhancing documentation and visual representations of workflows, sequences, or architectures.

Key Changes

• ZenUML Integration: The core of this update is the integration of ZenUML diagrams by importing and utilizing the @mermaid-js/mermaid-zenuml package. This allows for the inline definition of ZenUML diagrams within Markdown files, which are then rendered in the Markdown preview.
• Dependency Adjustments: added the @mermaid-js/mermaid-zenuml package as a dependency to enable the ZenUML diagram rendering functionality.
• Documentation Updates: Added external diagrams support section to the documentation to provide users with information on how to use ZenUML diagrams in their Markdown files.

[mjbvz]

Please open a linked issue too with example some mermaid for testing the new diagram type

[mjbvz]

Closing as we need an issue to track this and more explanation of why this is useful. I'd like more feedback from the community too before considering this