feat: Add SlackTimeScheduling new algorithm with Junit tests

[Hardvan]

• 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

All modified and coverable lines are covered by tests ✅

Project coverage is 69.64%. Comparing base (59a8e1d) to head (674f2cf).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #5814      +/-   ##
============================================
+ Coverage     69.61%   69.64%   +0.03%     
- Complexity     4701     4705       +4     
============================================
  Files           626      627       +1     
  Lines         17152    17169      +17     
  Branches       3314     3315       +1     
============================================
+ Hits          11940    11957      +17     
  Misses         4757     4757              
  Partials        455      455              

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