[Feature]: Add CrewAI example agent

Describe your feature request clearly: README lists CrewAI as a supported framework but there is no CrewAI example in the examples/ folder. All other listed frameworks (Agno, LangChain, LangGraph, AG2) already have examples. I'd like to add one for CrewAI.

How would you expect it to work? Add examples/crewai-agent/ with:

• A simple multi-agent CrewAI crew (2-3 agents with roles) wrapped with bindufy()
• README with setup instructions and curl recipe
• skill.yaml

The crew would take a user query and process it through multiple specialized agents, returning a final response via the A2A protocol.

Additional context: Contribute.md mentions "build one of the agents mentioned in the README" as a valid contribution. CrewAI is mentioned in README but has no working example yet.