Add Document QA Bot Example and Update README

[riteshravi1002]

Summary: This pull request introduces a new example of a Document QA Bot, demonstrating how to leverage large language models (LLMs) for extracting meaningful answers from documents. The example highlights the use of GPT-based models (including GPT-4 and Gemini 1.5 Pro) to provide accurate and contextually relevant responses based on document contents.

Changes Included in This PR:

Added a Document QA Bot example that enables question-answering based on document text.

Updated the README.md file to provide instructions for setting up and using the new Document QA Bot example.

Provided an overview of how the example works with different LLMs to process document data and answer user queries.

Motivation: This addition helps users understand how to build robust document-based question-answering systems. By incorporating GPT-based models, the example provides a scalable solution that can be extended to various document types, making it easier for developers to integrate LLMs into their document processing workflows.

How to Use:

Follow the instructions in the updated README.md to get started with the new example.

Learn how to configure the QA Bot to answer questions based on the document of your choice.