input: Write a function to take 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", "world of coding")==['Hello', 'world', 'world', 'of', 'coding']
  assert string_to_list("", "Empty string")==['Empty', 'string']
  assert string_to_list("Single", "")==['Single']
  assert string_to_list("", "")==[]
output: def string_to_list(s1, s2):
      return s1.split() + s2.split()