input: Write a function to take in two strings as input, and output a list of all the words in both strings. The function should split each string into a list of words and combine the two lists. If the given strings are empty, the function should return an empty list.
  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 is fun")==['Hello', 'world', 'Python', 'is', 'fun']
  assert string_to_list("", "")==[]
  assert string_to_list("One string", "")==['One', 'string']
  assert string_to_list("", "Another string")==['Another', 'string']
output: def string_to_list(str1, str2):
      if not str1 and not str2:
          return []
      words1 = str1.split()
      words2 = str2.split()
      return words1 + words2