refactor: Enhance docs, add more tests in AffineConverter

[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 83.33333% with 1 line in your changes missing coverage. Please review.

Project coverage is 70.52%. Comparing base (73416e2) to head (426f442).

Files with missing lines	Patch %	Lines
...com/thealgorithms/conversions/AffineConverter.java	83.33%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##             master    #5915   +/-   ##
=========================================
  Coverage     70.52%   70.52%           
- Complexity     4819     4820    +1     
=========================================
  Files           644      644           
  Lines         17454    17458    +4     
  Branches       3358     3359    +1     
=========================================
+ Hits          12310    12313    +3     
  Misses         4681     4681           
- Partials        463      464    +1     

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