Added Algorithm for Merging Two Sorted List in C++

[Mayank29903]

This program merges two sorted linked lists into a single sorted linked list using a simple comparison-based approach.

Each node of the list contains an integer value and a pointer to the next node.

The algorithm compares the elements of both lists one by one and adds the smaller one to the new merged list.

It efficiently handles different-sized lists and cases where one list becomes empty before the other.

Time Complexity: O(n + m) (where n and m are the sizes of the two lists)

Space Complexity: O(1) (in-place merge using existing nodes)