refactor: Enhance docs, add tests in StackOfLinkedList

[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

Attention: Patch coverage is 50.00000% with 3 lines in your changes missing coverage. Please review.

Project coverage is 69.13%. Comparing base (0f1dcbe) to head (4401bd1).

Files with missing lines	Patch %	Lines
...ithms/datastructures/stacks/StackOfLinkedList.java	50.00%	3 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #6021      +/-   ##
============================================
+ Coverage     69.07%   69.13%   +0.05%     
- Complexity     4665     4667       +2     
============================================
  Files           624      624              
  Lines         17166    17156      -10     
  Branches       3311     3309       -2     
============================================
+ Hits          11857    11860       +3     
+ Misses         4855     4844      -11     
+ Partials        454      452       -2     

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