Hole type: subroutine
Write a subroutine that accepts a list of words, and returns the list
sorted by the first *vowel* that appears in each word. If two words
have the same first vowel, it does not matter which is sorted first.
Words will be in lowercase and will always contain at least one vowel.
(Vowels are a, e, i, o, and u.)
e.g.: hole('dog', 'cat', 'fish', 'duck', 'lemur')
returns: ('cat', 'lemur', 'fish', 'dog', 'duck')