Add Maximum Subarray Sum Problem and Solution

[staging-devin-ai-integration]

Add Maximum Subarray Sum Problem and Solution

This pull request adds a new problem "Maximum Subarray Sum" to the algorithms repository. The problem and its solution have been implemented in the array folder.

Changes Made

1. Added README.md file with the problem statement, example, constraints, and task description.
2. Implemented the solution in solution.py using Kadane's Algorithm, which has O(n) time complexity.

Problem Overview

The Maximum Subarray Sum problem asks to find the contiguous subarray with the largest sum within a given integer array. This is a classic algorithmic problem that has applications in various fields, including finance and data analysis.

Solution Approach

The implemented solution uses Kadane's Algorithm, which efficiently solves the problem in O(n) time complexity. The algorithm makes a single pass through the array, keeping track of the maximum sum seen so far and the current sum.

Testing

A test case has been included in the solution.py file to verify the correctness of the implementation.

Link to Devin Run

This problem and solution were implemented as part of a Devin run. You can find the details of the run here:
https://staging.itsdev.in/devin/680d92315c42401488c938b18d574998

Please review the changes and provide any feedback or suggestions for improvement.

This Devin run was requested by Federico.