added two functions to convert between arrays and linked lists

[KyleMcIndoe]

theres a note at the start of the file with more details

 know more

Describe your change:

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

Checklist:

• [y ] I have read CONTRIBUTING.md.
• [y ] This pull request is all my own work -- I have not plagiarized.
• [y ] I know that pull requests will not be merged if they fail the automated tests.
• [ y] This PR only changes one algorithm file. To ease review, please open separate PRs for separate algorithms.
• [ y] All new JavaScript files are placed inside an existing directory.
• [ y] 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
• [ n]All new algorithms have a URL in its comments that points to Wikipedia or other similar explanation.
• [n ] If this pull request resolves one or more open issues then the commit message contains Fixes: #{$ISSUE_NO}.

[appgurueu]

Doesn't meet our the style requirements set by our contribution guidelines:

• Use a proper JSDoc comment. That JS isn't your primary language etc etc. is irrelevant to the code (you may include it in the discussion here on GH however).
• Yes, listnode should not be a function. You should integrate this with the existing linked list classes by adding a constructor that constructs a linked list from an array (this already exists, so you don't have to do it), and adding a method that turns the linked list into an array (if it doesn't exist).
• Use let (or const) over var
• Format your JS properly