Given two sentences, return whether they are shadows of each other. This means that all of the word lengths are the same, but the corresponding words don't share any common letters.
shadow_sentence("they are round", "fold two times") ➞ True
shadow_sentence("own a boat", "buy my wine") ➞ False
# No words share common letters, but "a" and "my" have different lengths.
shadow_sentence("his friends", "our company") ➞ False
# Word lengths are the same but "friends" and "company" share the letter "n".
shadow_sentence("salmonella supper", "birthright") ➞ False
# Setences with different numbers of words.
False if the sentences have different numbers of words.