[Self-Host] (documentation) CONTRIBUTING.md lacks documentation for using Docker Compose

[RutamBhagat]

Describe the Issue
The current CONTRIBUTING.md lacks documentation for using Docker Compose as a simpler alternative to run the project locally. While the current manual setup is helpful, we should add Docker Compose instructions since it's already supported via docker-compose.yaml.

Proposed Changes
Add a new section to CONTRIBUTING.md after the existing manual setup instructions:

### Alternative: Using Docker Compose

For a simpler setup, you can use Docker Compose to run all services with a single command:

1. Make sure you have Docker and Docker Compose installed
2. Copy the `.env.example` file to `.env` in the `/apps/api/` directory and configure as needed
3. From the root directory, run:

 ```bash
 docker compose up
 ```

This will start Redis, the API server, and workers automatically in the correct configuration.

You can then test the API just as described above:

Why This Change Matters

• Simpler developer onboarding
• Consistent environment across all developers
• No need to manage multiple terminal windows
• Reduces potential configuration issues

Additional Context
This change doesn't remove the existing manual setup instructions, but adds Docker Compose as an alternative option that some developers may prefer.

Related Files

• CONTRIBUTING.md
• docker-compose.yaml