Enhance class & function documentation in WordSearch.java

[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 55.05%. Comparing base (2cdd97c) to head (5766be1).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #5578      +/-   ##
============================================
- Coverage     55.07%   55.05%   -0.02%     
+ Complexity     3478     3476       -2     
============================================
  Files           539      539              
  Lines         15607    15607              
  Branches       2965     2965              
============================================
- Hits           8595     8592       -3     
- Misses         6655     6656       +1     
- Partials        357      359       +2     

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