[Term Entry] Affinity Diagram

[AnamolR]

Description

This PR adds a new UX research synthesis method titled Affinity Diagram to the uiux/concepts/ section.

New folder: content/uiux/concepts/affinity-diagram/
Markdown file: affinity-diagram.md introduces the concept of affinity diagrams, explains when they are used, how to build them, and the collaborative benefits they offer during the research synthesis process.

The entry includes a visual illustration of grouped sticky notes and aligns with other collaborative UX research and analysis tools in the Docs library.

Issues Solved

Closes #6602

Type of Change

Adding a new entry

Checklist

• All writings are my own.
• My entry follows the Codecademy Docs style guide.
• My changes generate no new warnings.
• I have performed a self-review of my own writing and code.
• I have checked my entry and corrected any misspellings.
• I have made corresponding changes to the documentation if needed.
• I have confirmed my changes are not being pushed from my forked main branch.
• I have confirmed that I'm pushing from a new branch named after the changes I'm making.
• I have linked any issues that are relevant to this PR in the Issues Solved section.