Add AI Marketing Agent project with implementation& data

[thehiddenrocky]

This PR adds an AI Marketing Agent implementation that:

• Implements market research analysis using Reddit data
• Uses LLM for insight generation
• Includes vector database storage
• Contains complete implementation with data

Files are contained within the AI-marketing-agent directory.

[NirDiamant]

Hi!
please add at the beginning of the tutorial introduction that describes the projects according to CONTRIBUTING.MD file

[NirDiamant]

The Reddit-based market research agent is a good tutorial. Please:

1. Move the notebook to all_agents_tutorials/ (not a separate AI-marketing-agent/ directory)
2. Consolidate the standalone .py files into the notebook for consistency with the rest of the repo
3. Add a README entry

Happy to merge once restructured.