Add Quick Sort algorithm

Feature Request

Add Quick Sort algorithm implementation to the sorting algorithms collection.

Requirements

• Implement Quick Sort with good performance characteristics
• Use optimization techniques to avoid worst-case scenarios on sorted/reverse sorted data
• Add comprehensive test coverage
• Update documentation in README
• Add to demo program in main.py

Technical Details

• Time Complexity: O(n log n) average, O(n²) worst case
• Space Complexity: O(log n) due to recursion stack
• Consider using median-of-three pivot selection for better performance

Acceptance Criteria

• Quick Sort function implemented in sort.py
• All tests pass including edge cases
• Algorithm registered with proper metadata
• README updated with complexity information
• Demo program includes Quick Sort