Implement sliding window algorithms for fixed and dynamic sizes with tests

[Kesavan-77]

Sliding Windows Algorithm

• Added maxSumSubarrayFixed function to calculate the maximum sum of a fixed-size subarray.
• Added longestSubarrayWithSumAtMost function to find the longest subarray with a sum less than or equal to a given target.
• Included tests for both functions to ensure correctness and edge case handling.
• Updated documentation to reflect the new implementations.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.80%. Comparing base (55ff0ad) to head (a3c5ac0).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1765      +/-   ##
==========================================
+ Coverage   84.76%   84.80%   +0.03%     
==========================================
  Files         378      380       +2     
  Lines       19738    19785      +47     
  Branches     2957     2965       +8     
==========================================
+ Hits        16731    16778      +47     
  Misses       3007     3007              

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[Kesavan-77]

@raklaptudirm , @appgurueu kindly check the above PR for merging.