Add contribution guidelines for bug fixes and feature requests

[Copilot]

The repository lacked documented contribution guidelines, specifically requirements for referencing issue numbers when fixing bugs and checking with maintainers before implementing features.

Changes

• CONTRIBUTING.md: Created comprehensive guide covering bug reporting, bug fixes (requiring issue references), feature implementations (requiring maintainer approval), and PR guidelines
• README.md: Added Contributing section linking to the new guidelines

Contributors now have clear expectations: bug fix PRs must reference issues, and feature work requires upfront maintainer approval.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Hello! Thank you for your contribution.</issue_title>
<issue_description>Hello! Thank you for your contribution.

If you are fixing a bug, please reference the issue number in the description.

If you are implementing a feature request, please check with the maintainers that the feature will be accepted first.

Originally posted by @github-actions in actions/first-interaction#393 (comment)</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Hello! Thank you for your contribution. #4

---

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.