Add palindrome utility function and corresponding tests

[callistoVII]

This Pull Request introduces a new utility function, isPalindrome, which determines whether a given string is a palindrome. This feature was implemented as part of Assignment 1.1, focusing on working within a feature branch, writing clean commits, and providing automated tests for validation.

The implementation includes:

A new utility file: src/utils/palindrome.js
A corresponding test suite: test/utils/palindrome.spec.js

The function normalizes input by lower-casing and removing non‑alphanumeric characters before performing the palindrome check. This ensures correct handling of mixed‑case strings, punctuation, and spacing.

No existing project files were modified.

Testing: Three unit tests were added to validate functionality.

Simple palindrome, verifies that a straightforward palindrome returns true.
Non-palindrome, ensures that a non-matching string returns false.
Punctuation/mixed-case palindrome, confirms correct behavior w/ normalized input.

To run test suite:
npm install
npm test

All tests pass successfully.

Note for Reviewers -
The feature is fully isolated to the add_palindrome_function branch. No changes were made to the project's main or existing utilities.

[slkueneke]

• Adding in comments would make the code a little clearer for someone updating, extending, or maintaining this function
• Instead of returning false when the value passed is not a string, throw a descriptive error so the function's return value differentiates between passing a non-string value and a string that is not a palindrome (both currently return the same value of false).
• It might be clearer to name the files (utility and corresponding tests) the same name as the function for quick finding and consistency.
• Add in a 4th unit test for the use case when a non-string value is passed to the function.