refactor: Enhance docs, add more tests in `TwosComplement`

[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 70.29%. Comparing base (ef7f2e9) to head (66b5d27).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #5862      +/-   ##
============================================
- Coverage     70.30%   70.29%   -0.01%     
+ Complexity     4765     4764       -1     
============================================
  Files           635      635              
  Lines         17307    17306       -1     
  Branches       3331     3330       -1     
============================================
- Hits          12167    12166       -1     
  Misses         4680     4680              
  Partials        460      460              

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