Added a linear system solver

[21kondav]

• 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 87.50000% with 4 lines in your changes missing coverage. Please review.

Project coverage is 73.57%. Comparing base (769e497) to head (53e8790).

Files with missing lines	Patch %	Lines
...ain/java/com/thealgorithms/matrix/SolveSystem.java	87.50%	2 Missing and 2 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #6196      +/-   ##
============================================
+ Coverage     73.55%   73.57%   +0.01%     
- Complexity     5220     5227       +7     
============================================
  Files           667      668       +1     
  Lines         18067    18099      +32     
  Branches       3487     3496       +9     
============================================
+ Hits          13290    13317      +27     
- Misses         4249     4251       +2     
- Partials        528      531       +3     

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[DenizAltunkapan]

Looks good to me! 🔥 just tested it with some own matrices.

[siriak]

Looks good, thanks!