📖 fix(docs): newlines in `docs/contributing.md`

[koibtw]

Type of Change

• [x] Bug fix
• [x] Documentation update
• [x] Hotfix

Description

Using echo -e to display \ns correctly.

Issues / other PRs related

• Resolves #795

Checklist

• [x] My code adheres to the coding and style guidelines of the project.
• [x] I have performed a self-review of my own code.
• [x] I have made corresponding changes to the documentation.
• [x] My changes generate no errors/warnings/merge conflicts.