[FEATURE]: Add Kahn's Algorithm in Graphs #1795

[Virus2hell]

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Describe your change:

• [x] Add an algorithm?
• [ ] Fix a bug or typo in an existing algorithm?
• [ ] Documentation change?

Algorithm added: Kahn's Algorithm (Topological Sort using BFS)

Motivation: Kahn's Algorithm is a canonical graph algorithm for topological sorting of Directed Acyclic Graphs (DAGs). It was missing in the repository.

Checklist:

• [x] I have read CONTRIBUTING.md.
• [x] This pull request is all my own work -- I have not plagiarized.
• [x] I know that pull requests will not be merged if they fail the automated tests.
• [x] This PR only changes one algorithm file (KahnsAlgorithm.js and its test).. To ease review, please open separate PRs for separate algorithms.
• [x] All new JavaScript files are placed inside an existing directory.
• [x] All filenames should use the UpperCamelCase (PascalCase) style. There should be no spaces in filenames. Example:UserProfile.js is allowed but userprofile.js,Userprofile.js,user-Profile.js,userProfile.js are not
• [x] All new algorithms have a URL in their comments that points to Wikipedia or another similar explanation.
• [x] If this pull request resolves one or more open issues then the commit message contains Fixes: #1795 .

[codecov-commenter]

Codecov Report

:white_check_mark: All modified and coverable lines are covered by tests. :white_check_mark: Project coverage is 85.93%. Comparing base (08d8c6b) to head (7d025a7).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1796      +/-   ##
==========================================
+ Coverage   85.91%   85.93%   +0.02%     
==========================================
  Files         379      380       +1     
  Lines       19778    19807      +29     
  Branches     3015     3026      +11     
==========================================
+ Hits        16993    17022      +29     
  Misses       2785     2785              

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