Create a function that takes a string (without spaces) and a word list, cleaves the string into words based on the list, and returns the correctly spaced version of the string (a sentence). If a section of the string is encountered that can't be found on the word list, return "Cleaving stalled: Word not found".
word_list = ["about", "be", "hell", "if", "is", "it", "me", "other", "outer", "people", "the", "to", "up", "where"]
cleave("ifitistobeitisuptome", word_list) ➞ "if it is to be it is up to me"
cleave("hellisotherpeople", word_list) ➞ "hell is other people"
cleave("hellisotterpeople", word_list) ➞ "Cleaving stalled: Word not found"
Words on the word_list can appear more than once in the string. The word_list is a reference guide, kind of like a dictionary that lists which words are allowed.