feat(docs): Implement automatic graph documentation generation

[plfavreau]

🚀 What's new?

This PR adds automatic graph documentation generation for the LangGraph structure. Specifcally, it adds a new github workflow to automatically update graph visualization when graph structure changes :

• Created Python script to generate graph visualization as PNG using Mermaid
• Updated README with a new "Agentic System Overview" section displaying the graph
• Added necessary dependencies and configurations for graph generation
• Configured workflow to commit and push changes automatically, only when the graph is updated.

🤔 Type of Change

What kind of change is this? Mark with an x

• Bug fix (non-breaking change that solves an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation (update to the docs)

✅ Checklist

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• I have read the Contributing Guide.
• My code follows the project's style guidelines (ruff check . and ruff format . pass).
• I have added necessary documentation (if applicable).

💬 Any questions or comments?

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[KYN4]

Perfect! Very handy workflow :D