refactor: Enhance docs, add tests in `TarjansAlgorithm`

[Hardvan]

• [x] I have read CONTRIBUTING.md.
• [x] This pull request is all my own work -- I have not plagiarized it.
• [x] All filenames are in PascalCase.
• [x] All functions and variable names follow Java naming conventions.
• [x] All new algorithms have a URL in their comments that points to Wikipedia or other similar explanations.
• [x] 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 :white_check_mark:

Project coverage is 71.68%. Comparing base (474e0de) to head (5583a4f).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #5970      +/-   ##
============================================
- Coverage     71.68%   71.68%   -0.01%     
+ Complexity     4946     4945       -1     
============================================
  Files           650      650              
  Lines         17565    17565              
  Branches       3384     3384              
============================================
- Hits          12592    12591       -1     
  Misses         4499     4499              
- Partials        474      475       +1     

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