Adding method to check wether a matrix is stochastic

[Dsannue]

• 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

❌ Patch coverage is 76.00000% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 78.91%. Comparing base (51335cc) to head (e085cfc).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
...ava/com/thealgorithms/matrix/StochasticMatrix.java	76.00%	3 Missing and 3 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #7184      +/-   ##
============================================
- Coverage     78.92%   78.91%   -0.02%     
- Complexity     6875     6884       +9     
============================================
  Files           773      774       +1     
  Lines         22722    22747      +25     
  Branches       4461     4469       +8     
============================================
+ Hits          17933    17950      +17     
- Misses         4073     4077       +4     
- Partials        716      720       +4     

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