Create a function which validates whether a 3 character string is a vowel sandwich. In order to have a valid sandwich, the string must satisfy the following rules:
is_vowel_sandwich("cat") ➞ True
is_vowel_sandwich("ear") ➞ False
is_vowel_sandwich("bake") ➞ False
is_vowel_sandwich("try") ➞ False
False if the word is not 3 characters in length.