feat: FindMiddleNode in a Linked List Algorithm

[BKarthik7]

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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.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.68%. Comparing base (9010481) to head (ef7634d).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1701      +/-   ##
==========================================
+ Coverage   84.65%   84.68%   +0.03%     
==========================================
  Files         378      379       +1     
  Lines       19744    19784      +40     
  Branches     2951     2956       +5     
==========================================
+ Hits        16715    16755      +40     
  Misses       3029     3029              

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[BKarthik7]

@raklaptudirm @appgurueu Can you review my code and tag it as hactoberfest

[appgurueu]

Redundant with

JavaScript/Data-Structures/Linked-List/SinglyLinkedList.js

Lines 218 to 229 in 9010481

	// Returns a reference to middle node of linked list
	findMiddle() {
	// If there are two middle nodes, return the second middle node.
	let fast = this.headNode
	let slow = this.headNode
	while (fast !== null && fast.next !== null) {
	fast = fast.next.next
	slow = slow.next
	}
	return slow
	}