Feat: TwoSum function created with test cases

[developerr-ayush]

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Describe your change:

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

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 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
• All new algorithms have a URL in their comments that points to Wikipedia or another similar explanation.
• If this pull request resolves one or more open issues then the commit message contains Fixes: #{$ISSUE_NO}.

[developerr-ayush]

hey i have registered in Hacktoberfest so does this count?

[appgurueu]

• You should use a proper JSDoc comment.
• The Map should actually be an ES6 Map (rather than a dictionary which coerces keys to strings).
• You should use Jest's each for the test cases. I'd probably divide them into two sets, one of tests without and the other of tests with a solution for the two sum problem.

[developerr-ayush]

i have made the following changes if I am wring at some please them can you let me know.