Add an schematic of the graph to the docs

[filipeximenes]

From the quick start

from IPython.display import Image, display

try:
    display(Image(graph.get_graph().draw_mermaid_png()))
except Exception:
    # This requires some extra dependencies and is optional
    pass

[fjsj]

It's nice to document and display the langgraph's graph. But I would like a excalidraw for the whole architecture as well. It should show:

• Frontend (React, HTMX, etc.)
  • Django AI Assistant client
• Backend
  • Django AI Assistant API
    • LangGraph
    • LLM provider