[sarthakgupta1907-cell]

Describe your change:

Add implementation of the Perfect Number algorithm in Maths/PerfectNumber.js.

A perfect number is a positive integer equal to the sum of its proper divisors.

• Example: 6 = 1 + 2 + 3 ✓
• Example: 28 = 1 + 2 + 4 + 7 + 14 ✓

Checklist:

• I have read CONTRIBUTING. md.
• This pull request is all my own work—I have not plagiarized.
• I know that pull requests will not be merged if they fail the automated tests.
• This PR only changes one algorithm file. To ease review, please open separate PRs for separate algorithms.
• All new JavaScript files are placed inside an existing directory.
• All filenames are in the format MyAlgorithmName.js -- PascalCase.
• All new algorithms have a URL in their comments that points to Wikipedia or another similar explanation.
• All new algorithms have tests, and the tests pass.
• All code is formatted with npx standard --fix .

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.91%. Comparing base (5c39e87) to head (db479a4).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1919      +/-   ##
==========================================
- Coverage   85.91%   85.91%   -0.01%     
==========================================
  Files         379      379              
  Lines       19778    19776       -2     
  Branches     3016     3020       +4     
==========================================
- Hits        16993    16991       -2     
  Misses       2785     2785              

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