input: Write a python function to convert two space-separated strings into a single list of words.
  assert string_to_list("I want to make a difference", "The journey to success is long") == ['I', 'want', 'to', 'make', 'a', 'difference', 'The', 'journey', 'to', 'success', 'is', 'long']
  assert string_to_list("Hello world", "Python programming") == ['Hello', 'world', 'Python', 'programming']
  assert string_to_list("A quick brown fox", "jumps over the lazy dog") == ['A', 'quick', 'brown', 'fox', 'jumps', 'over', 'the', 'lazy', 'dog']
output: def string_to_list(str1, str2):
      return str1.split() + str2.split()