feat: autogen llama-stack-client CLI reference doc (#190)

# What does this PR do?

- Add script to autogen CLI reference doc

[//]: # (If resolving an issue, uncomment and update the line below)
[//]: # (Closes #[issue-number])

## Test Plan
```
python scripts/gen_cli_doc.py
```

[//]: # (## Documentation)
[//]: # (- [ ] Added a Changelog entry if the change is significant)

Author: yanxi0830