input: Write a python function to count the occurrence of each word in a list of strings and return the most common words.
  assert count_words(["the quick brown fox", "jumped over the lazy dog"]) == [('the', 2), ('quick', 1), ('brown', 1), ('fox', 1), ('jumped', 1), ('over', 1), ('lazy', 1), ('dog', 1)]
  assert count_words(["hello world", "hello"]) == [('hello', 2), ('world', 1)]
  assert count_words(["test test test", "test test"]) == [('test', 5)]
output: def count_words(strings):
      from collections import Counter
      
      all_words = ' '.join(strings).split()
      word_counts = Counter(all_words)
      return word_counts.most_common()