emoji_eventsRoman numerals

Write to_roman(n) that turns a whole number from 1 to 3999 into Roman numerals.

• Use the subtractive forms: 4 is "IV", 9 is "IX", 40 is "XL", 900 is "CM".
• Raise ValueError for numbers outside 1–3999.

Acceptance criteria

• to_roman(1994) returns "MCMXCIV".
• The tests at the bottom print All tests passed.

Hint: walk a table of (value, symbol) pairs from largest to smallest.