Formatting: Add function to format number to its roman number

[Farkhanda-Dalal]

Description:
The formatRomanNumeral(num) function will convert a positive integer into its Roman numeral representation.
It should support values from 1 up to at least 3999 (standard Roman numeral system).

Acceptance Criteria:

1     → "I"
4     → "IV"
9     → "IX"
58    → "LVIII"      // (50 + 5 + 3)
1994  → "MCMXCIV"    // (1000 + 900 + 90 + 4)
2025  → "MMXXV"
3999  → "MMMCMXCIX"
0     → ""           // return empty string or throw error for 0
-5    → Error        // invalid input
"123" → Error        // must be number

The function must:

• Handle all valid integers in the range 1–3999.
• Use subtractive notation (e.g., IV for 4, IX for 9, XL for 40, CM for 900).
• Return an empty string or throw an error for 0 and negative numbers.
• Throw a TypeError if the input is not a number.
• Include comprehensive unit tests for edge cases (1, 4, 9, 3999, invalid inputs).