Added example for docling

[rushi-sathe]

• Adds a new Python 3.12 RAG example using docling-parse for PDF parsing and text extraction
• Demonstrates document chunking and keyword-based retrieval workflow
• Includes sample PDF generation and end-to-end integration example
• Adds installation script, documentation, and dependency setup files
• Provides comprehensive test coverage with all 9 tests passing
• Tests are generated using BOB