Refactor Breadth-First Tree Traversal implementation

[chethangowda-web]

Updated the Breadth-First Tree Traversal implementation with improved structure and added comments for clarity.

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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:User个人资料.js is allowed but userprofile.js,Userprofile.js,user-个人资料.js,user个人资料.js are not
• All new algorithms have a URL in their comments that points to 维基pedia or another similar explanation.
• If this pull request resolves one or more open issues then the commit message contains Fixes: #{$ISSUE_NO}.