Added Merge Sort algorithm in Python

[Husnain-Ali-24]

Description of Changes:
Added a Python implementation of the Merge Sort algorithm in mergesort.py. This algorithm sorts an array by dividing it into two halves, recursively sorting each half, and then merging the sorted halves together.

Problem Statement:
Implement the Merge Sort algorithm to sort a list of numbers in ascending order.

Algorithm Details:

• Complexity:
  • Time Complexity: (O(n \log n)), where (n) is the number of elements in the list. This complexity holds for both average and worst cases.
  • Space Complexity: (O(n)), due to the auxiliary space used for merging.
• Explanation:
  • The list is divided into two halves recursively until each sublist has a single element.
  • The sorted sublists are then merged back together to form a single sorted list.