Add Sliding Window XOR algorithm in C++ with test cases

[DataWorshipper]

Description of Change

This pull request adds a C++ implementation of the Sliding Window XOR problem to the Bit Manipulation section.

The algorithm calculates the bitwise XOR of every window of size k in an array of n integers generated using the recurrence relation:

The array of size n is generated using the recurrence:

arr[0] = x;                 // first element
arr[i] = (a * arr[i-1] + b) % c;  // for i = 1 to n-1

It maintains a sliding window of size k using two pointers, efficiently computing the cumulative XOR of all windows in O(n) time with O(n) space.

The submission is self-contained, with detailed Doxygen documentation and a test() function that includes multiple verified test cases to ensure correctness.

Checklist

• Added description of change
• Added file name matches File name guidelines
• Added tests and example, test must pass
• Added documentation so that the program is self-explanatory and educational
• Relevant documentation/comments is changed or added
• PR title follows semantic commit guidelines
• Search previous suggestions before making a new one, as yours may be a duplicate
• I acknowledge that all my contributions will be made under the project's license

Notes: Adds an O(n) solution for computing cumulative XOR of sliding windows in arrays of size n using a two-pointer technique. Includes self-test cases and detailed documentation.

[DataWorshipper]

I need to change some things in the pr