Add Gemini Flash 2.0 Integration with Lifecycle Methods to Chainlit Cookbook

[rawbear86342]

I would like to propose adding an integration with Gemini Flash 2.0 to the Chainlit cookbook.

This integration will enhance the ability to interact with Google's generative AI models and allow users to create conversational experiences with Gemini models.

Changes Proposed:

• Gemini Flash 2.0 Integration: Added support for the latest version of Gemini Flash 2.0 API.
• Lifecycle Methods: Added several lifecycle methods to handle messaging and feedback, such as:
• on_message: A function to handle incoming messages and respond using Gemini Flash 2.0.