[Edit] Problem Statement: Add Key Elements and Examples

[AnamolR]

Description

This PR updates the existing Problem Statement entry in the uiux/concepts/problem-statement section to include two new content sections: Key Elements and Example Problem Statements.

The additions provide clearer guidance on how to structure effective problem statements and illustrate real-world examples to support understanding and application concisely. These updates improve the educational value and practical utility of the entry in addition to the existing short definition.

Issues Solved

Type of Change

Editing an existing entry (fixing a typo, bug, issues, etc)

Checklist

• All writings are my own.
• My edits follow 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 the updated content 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.