Add algorithms for 2Sum, 3Sum, Kadane's Algorithm, and linked list pr…

[karankumar12345]

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

Description: This pull request adds algorithms for 2Sum, 3Sum, Kadane's Algorithm, and linked list problems including finding the intersection point and implementing the slow-fast pointer technique.

1. 2Sum Algorithm: Finds two numbers in an array that add up to a specified target sum using a hash map for efficient lookups.
2. 3Sum Algorithm: Identifies all unique triplets in the array that sum to zero.
3. Kadane's Algorithm: Efficiently computes the maximum sum of a contiguous subarray.
4. Linked List Problems:
   • FindIntersectionPoint: Determines the intersection point of two linked lists.
   • SlowFast: Implements the slow-fast pointer technique to detect cycles in a linked list.

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. To ease review, please open separate PRs for separate algorithms.
• [x] All new JavaScript files are placed inside an existing directory.
• [x] All filenames 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.
• [ ] If this pull request resolves one or more open issues, then the commit message contains Fixes: #{$ISSUE_NO}. (Replace {$ISSUE_NO} with the actual issue number if applicable) .

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 84.77%. Comparing base (18da83a) to head (2029064).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1716      +/-   ##
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+ Coverage   84.65%   84.77%   +0.11%     
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  Files         378      382       +4     
  Lines       19744    19895     +151     
  Branches     2951     2978      +27     
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+ Hits        16715    16866     +151     
  Misses       3029     3029              

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