Add Quick Sort algorithm

Task

Implement Quick Sort algorithm for the python-sort-algorithm project.

Requirements

• Implement quick_sort() function with O(n log n) average time complexity
• Use median-of-three pivot selection to avoid worst-case performance
• Follow project conventions for non-mutating sort functions
• Add comprehensive tests
• Update documentation

Acceptance Criteria

• Quick Sort implementation passes all tests
• Algorithm is registered in test suite
• Documentation is updated with complexity information
• Demo in main.py includes Quick Sort