docs: placeholder section for clean code DRAFT

[liammoat]

Pull Request Template

What are you trying to address

• Introduce a new section for "Code Quality".
• Provide a summary of "Clean Code" and it's important in Engineering Fundamentals.

Checklist

[READY TO PR? Use the check-list below to ensure your branch is ready for PR.]

• Changes follow the repo structure and land in the appropriate folder and section
• No confidential information
• No duplicated content
• Labeled appropriately
• Added 2 reviewers
• No lint errors
• No lint check errors related to your changes

Note: You may see link check errors on pages you have not touched. This is normal, and due to either broken links or sites that reject link checker bots. The reviewer will help you get to a green state on these.