Add a CONTRIBUTING.md file

[shashaBot]

Hi 👋

I’d like to propose adding a CONTRIBUTING.md file to the repository to help onboard new contributors and clarify the contribution process (e.g., how to run tests, coding style, when to open issues first, etc.).

This can make it easier for folks to get involved and ensure consistency across contributions.

I’ll be creating a PR for this shortly. Let me know if there’s anything you’d like me to include or if you have specific guidelines you’d prefer to highlight. Let me know if I should also add a pull_request_template.md so you have consistency in the contributions as well.

Thanks!