Added langgraph example

[cnemri]

Title: Add "Agentic Accessibility Checker" Demo

Description:
This pull request introduces a new demo to the AAIE samples repo: the Agentic Accessibility Checker. The demo provides an end-to-end example of building an autonomous agent for real estate accessibility analysis using Google’s cutting-edge AI tools, including Gemini and the Vertex AI Reasoning Engine. It includes:

• Synthetic Data Generation: Utilizes generative models to create realistic multimodal real estate data (text and images), stored in GCS and Firestore.
• Cloud Run API: A FastAPI-based service acting as the agent’s environment for retrieving property details.
• LangGraph Agent with Gemini: A ReAct-style agent that can reason about and interact with data, tools, and APIs, leveraging both text and image understanding capabilities.
• Streamlit Frontend: A user-friendly interface that allows interactive exploration of properties and direct engagement with the agent.
• Comprehensive Setup Instructions: Detailed steps for installation, data generation, API deployment, agent deployment, and frontend setup, ensuring a smooth onboarding experience.
• Integration with Google Cloud Services: integrates with Firestore, GCS, and Vertex AI Reasoning Engine, includes environment-specific parameters.

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[RajeshThallam]

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[RajeshThallam]

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