feat(slidingwindow): add SmallestSubarrayWithSum and its tests

[nihalsingh373]

dded an efficient sliding window solution for finding the smallest subarray with a sum >= target, along with unit tests.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 81.81818% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 78.35%. Comparing base (bb6385e) to head (e671ff0).

Files with missing lines	Patch %	Lines
...orithms/slidingwindow/SmallestSubarrayWithSum.java	81.81%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##             master    #6989   +/-   ##
=========================================
  Coverage     78.35%   78.35%           
- Complexity     6615     6620    +5     
=========================================
  Files           746      747    +1     
  Lines         22015    22026   +11     
  Branches       4320     4323    +3     
=========================================
+ Hits          17249    17259   +10     
- Misses         4078     4079    +1     
  Partials        688      688           

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