Request: Add contribution guidelines

[lets-build-an-ocean]

Hello,

I'm interested in contributing to this project and noticed there are no formal contribution guidelines (CONTRIBUTING.md).

It would be helpful to have documentation covering:

• Code style and conventions
• Commit message format preferences
• Testing requirements
• Pull request process
• Development setup instructions

This would make it easier for new contributors to submit quality contributions that align with the project's standards.

Thank you for maintaining this excellent WebSocket library!