Feature: Implement Mermaid.js Rendering for Diagrams

[ImGajeed76]

Description:

To enhance Axonotes' capabilities as a comprehensive academic hub, this issue proposes the integration of Mermaid.js rendering. This would allow users to create and embed various diagrams (flowcharts, sequence diagrams, Gantt charts, etc.) directly within their notes using a simple text-based syntax.

Acceptance Criteria:

1. Users can input Mermaid syntax (e.g., within a dedicated code block like ```mermaid ... ```).
2. The Axonotes editor correctly renders the Mermaid syntax into a visual diagram inline.
3. Supported diagram types should ideally include (but not be limited to): flowchart, sequence, class, state, ERD, and Gantt charts.
4. The rendered diagrams are viewable within Axonotes across platforms.
5. Exported documents (e.g., PDF) should ideally include the rendered diagrams as images.

Benefits:

• Enhanced Note-Taking & Content Creation: Directly supports "Powerful Note-Taking & Content Creation" by adding a versatile visualization tool.
• Unifying Workflow: Reduces the need for users to switch to external diagramming applications, aligning with the core goal of a "Central Academic Hub."
• Improved Learning & Teaching: Facilitates clearer explanations and understanding of complex topics.
• Complements Existing Features: Builds upon "Rich Content Integration" alongside LaTeX and code snippets.

Additional Context:

This feature would significantly boost the utility of Axonotes for technical subjects, project planning, and general knowledge organization, fitting well with the vision of a comprehensive academic suite.