Added the Goldbach's Conjecture algorithm

[BILLSARAN]

• 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 0% with 18 lines in your changes missing coverage. Please review.

Project coverage is 73.70%. Comparing base (1e6ed97) to head (7892341).

Files with missing lines	Patch %	Lines
...va/com/thealgorithms/maths/GoldbachConjecture.java	0.00%	18 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #6126      +/-   ##
============================================
- Coverage     73.78%   73.70%   -0.09%     
+ Complexity     5119     5118       -1     
============================================
  Files           658      659       +1     
  Lines         17632    17650      +18     
  Branches       3391     3397       +6     
============================================
- Hits          13010    13009       -1     
- Misses         4118     4136      +18     
- Partials        504      505       +1     

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