Add IntroSort Algorithm in R

[Siddhram]

This PR introduces a fully documented implementation of IntroSort in R, a hybrid sorting algorithm designed for robust performance and adaptive behavior on numeric vectors.

Overview

The intro.sort function combines three sorting strategies:

• Quick Sort for general partitioning
• Heap Sort when recursion depth exceeds a safe limit
• Insertion Sort for small partitions

This hybrid approach ensures O(n log n) worst-case performance while maintaining excellent average-case efficiency. It is particularly suitable for sorting arrays where performance consistency is important.

Features

• Hybrid sorting algorithm: Quick Sort + Heap Sort + Insertion Sort
• Automatically switches to Heap Sort on deep recursion
• Efficiently sorts small partitions with Insertion Sort
• Handles numeric vectors of arbitrary length
• Includes example usage at the bottom of the script
• Follows consistent API style with other R sorting algorithms

Complexity

• Time Complexity: O(n log n) worst-case; O(n log n) average-case
• Space Complexity: O(log n) due to recursion