input: Write a function to take in two strings as input and return a list of all the words in both strings.
  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", "Goodbye world")==['Hello', 'world', 'Goodbye', 'world']
  assert string_to_list("", "Empty string test")==['Empty', 'string', 'test']
  assert string_to_list("SingleWord", "AnotherSingleWord")==['SingleWord', 'AnotherSingleWord']
  assert string_to_list("Separated by commas", "and spaces")==['Separated', 'by', 'commas', 'and', 'spaces']
output: def string_to_list(str1, str2):
      return str1.split() + str2.split()