[Term Entry] First Click Test

[AnamolR]

Description

This PR adds a new usability testing method entry titled First Click Test to the uiux/concepts/first-click-test section.

New folder: content/uiux/concepts/first-click-test/
Markdown file: first-click-test.md introduces the method, outlines what it measures, and explains how it helps evaluate interface clarity, information hierarchy, and user navigation decisions.

This entry is consistent with other user research methods and testing technique documents in the Docs catalog.

Issues Solved

Closes #6595

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.