[Docs]: LlamaIndex support documentation

### 📘 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.