refactor: Enhance docs, add tests in QuickSortLinkedList

[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 (5246f63) to head (aa37020).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #5998      +/-   ##
============================================
- Coverage     67.98%   67.97%   -0.01%     
  Complexity     4586     4586              
============================================
  Files           620      620              
  Lines         17116    17114       -2     
  Branches       3305     3305              
============================================
- Hits          11636    11633       -3     
  Misses         5035     5035              
- Partials        445      446       +1     

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