[Docs]: LlamaIndex support documentation

[areibman]

📘 Current State of Documentation

We currently support LlamaIndex integration but are missing docs

📖 Suggested Improvement

1. Add missing docs to LlamaIndex - https://docs.llamaindex.ai/en/stable/api_reference/callbacks/agentops/
2. Update LlamaIndex docs with AgentOps latest patterns and screenshots https://docs.llamaindex.ai/en/stable/module_guides/observability/#agentops
3. Add LlamaIndex support to our own docs

🔗 Affected Documentation Pages

No response

🔍 Additional Context

No response

🤝 Contribution

• Yes, I'd be happy to submit a pull request with these changes.
• I need some guidance on how to contribute.
• I'd prefer the Agentops team to handle this update.