JavaScript Roman Numeral Converter

A lightweight, dependency-free JavaScript utility providing two functions — `toRoman` and `fromRoman` — to convert integers (1–3999) to Roman numerals and back. The `toRoman` function uses a standard mapping array with subtractive notation, while `fromRoman` applies right-to-left character comparison to handle combinations like IV and CM. Both functions include input validation and run in O(1) time complexity.