Add Sliding Window algorithm and tests for maximum sum of subarray

[Chiefpatwal]

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized it.
• All filenames are in PascalCase.
• All functions and variable names follow Java naming conventions.
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[codecov-commenter]

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[Chiefpatwal]

This pull request introduces a new module for the Sliding Window technique, including both the main implementation and the corresponding unit tests. The primary feature added is the MaxSumKSizeSubarray algorithm, which efficiently calculates the maximum sum of a subarray of a fixed size kk within a given array. The implementation follows best practices and includes comprehensive tests to ensure correctness and performance. I look forward to your feedback and suggestions for further improvements.

[siriak]

Looks good, thanks!