Add Quick Sort Algorithm

Description

Add quick sort algorithm implementation to the sorting algorithms collection.

Requirements

• Implement quick_sort function with optimal pivot selection
• Add comprehensive test coverage
• Update demo to include quick sort
• Document time and space complexity

Technical Details

• Time complexity: O(n log n) average, O(n²) worst case
• Space complexity: O(log n) due to recursion stack
• Use median-of-three pivot selection to avoid worst case on sorted arrays

Acceptance Criteria

• Quick sort function implemented
• All tests pass
• Demo updated
• Code follows project conventions