Write a function that sorts each string in an array by the letter in alphabetic ascending order (a-z).
sortByLetter(["932c", "832u32", "2344b"])
➞ ["2344b", "932c", "832u32"]
sortByLetter(["99a", "78b", "c2345", "11d"])
➞ ["99a", "78b", "c2345", "11d"]
sortByLetter(["572z", "5y5", "304q2"])
➞ ["304q2", "5y5", "572z"]
sortByLetter([])
➞ []