Add SlidingWindowExample class for max sum subarray

[debojyoti10CC]

• [ ] 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.
• [ ] All new algorithms have a URL in their comments that points to Wikipedia or other similar explanations.
• [ ] All new code is formatted with clang-format -i --style=file path/to/your/file.java

[codecov-commenter]

Codecov Report

:white_check_mark: All modified and coverable lines are covered by tests. :white_check_mark: Project coverage is 78.06%. Comparing base (48ba1ae) to head (5f5dd98).

Additional details and impacted files

@@            Coverage Diff            @@
##             master    #6918   +/-   ##
=========================================
  Coverage     78.05%   78.06%           
- Complexity     6466     6467    +1     
=========================================
  Files           738      738           
  Lines         21585    21585           
  Branches       4220     4220           
=========================================
+ Hits          16849    16851    +2     
+ Misses         4064     4063    -1     
+ Partials        672      671    -1     

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