fix: Restructure knowledge-check.md to match standard format

Moved answers from bottom into individual <details> tags after each question.

Changes:
- Removed single 'Answers' section at bottom with all answers
- Added <details> tag with 'Click to reveal answer' after each question
- Format now matches other knowledge check files (azure-arc, azure-local, etc.)
- Consistent formatting: 'Correct Answer: X' followed by Explanation and Reference

This provides better UX - learners can reveal each answer individually
instead of seeing all answers at once at the bottom of the page.

Author: jonathan-vella