refactor: Enhance docs, add tests in Kruskal

[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 67.97%. Comparing base (578e5a7) to head (2b63528).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #5967      +/-   ##
============================================
+ Coverage     67.69%   67.97%   +0.28%     
- Complexity     4577     4587      +10     
============================================
  Files           620      620              
  Lines         17145    17119      -26     
  Branches       3311     3306       -5     
============================================
+ Hits          11606    11637      +31     
+ Misses         5093     5037      -56     
+ Partials        446      445       -1     

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