Imagine a simple product catalog filter where you need to count how many items match a chosen rule. Write a function count_matches where each item is a list of three strings: type, color, and name. The rule_key is one of "type", "color", or "name", and rule_value is the value to match. Return the number of items whose selected field equals rule_value.

def count_matches(items: list[list[str]], rule_key: str, rule_value: str) -> int: