Update Issue Reporting and Pull Request Guidelines in CONTRIBUTING.md

Description:

Update CONTRIBUTING.md to emphasize the practice of always referencing the issue a PR addresses. If no issue exists, the contributor should create one before opening the PR.

What should be done

Issue Reporting:

Highlight that every bug or feature should be tracked as an issue in the github.

Guide contributors to create a new issue before starting to implement the PR resolves it.

Pull Request Guidelines:

Instruct that every PR must reference the corresponding issue (e.g., “Resolves/Closes #161”).

Explain that this improves organization, allows maintainers and other contributors to track progress, and enables evaluating the necessity of the implementation before any development effort, as mantainers and other contributors can see and talk about it before it's developed.

Clarify that referencing the issue also triggers GitHub’s automatic notifications, so other users can see that work is already in progress and avoid duplicating effort—even if the PR hasn’t been reviewed or marked as resolved yet.

Benefits:

Clear project organization and traceability of changes.

Easier review and prioritization of contributions.

Prevents unnecessary work on PRs that lack a clear rationale or confirmed need.

Helps contributors and maintainers see ongoing work in real time via GitHub notifications.

Review CONTRIBUTING.md, especially its issue-reporting and pull-request guidance. Update it to require an issue before implementation and an issue reference in every PR, including the organization, review, notification, and duplicate-work benefits. The work is done when these expectations are clearly documented in that file.