Create a function that takes an array of strings and returns the words that are exactly four letters.
IsFourLetters(["Tomato", "Potato", "Pair"]) ➞ ["Pair"]
IsFourLetters(["Kangaroo", "Bear", "Fox"]) ➞ ["Bear"]
IsFourLetters(["Ryan", "Kieran", "Jason", "Matt"]) ➞ ["Ryan", "Matt"]You can expect valid strings for all test cases.