add contributor onboarding guide for SDK, MCP, and npm SDK #11
Description
Summary
New contributors need a clearer map of the repository and contribution paths.
Problem
The repo now spans:
- Python SDK
- MCP server
- docs and examples
- planned npm SDK
Contributors need one guide that explains where to start.
Acceptance criteria
- contributor guide explains repo areas
- local setup is documented
- Redis and Circle sandbox expectations are documented
- guidance exists for picking issues and opening PRs