Adding PiApproximation algo

[the-yash-rajput]

• 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 89.47368% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 75.68%. Comparing base (f9a9ccb) to head (c1a497d).
⚠️ Report is 10 commits behind head on master.

Files with missing lines	Patch %	Lines
.../java/com/thealgorithms/maths/PiApproximation.java	89.47%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #6602      +/-   ##
============================================
+ Coverage     75.18%   75.68%   +0.50%     
- Complexity     5615     5745     +130     
============================================
  Files           690      698       +8     
  Lines         19408    19713     +305     
  Branches       3756     3822      +66     
============================================
+ Hits          14592    14920     +328     
+ Misses         4248     4215      -33     
- Partials        568      578      +10     

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