input: Write a python function to split the string 'joined_string' into two separate words based on the capital letter and return them as a list.
  assert split_joined_string('Programmingpython') == ['Programming', 'python']
  assert split_joined_string('HelloWorld') == ['Hello', 'World']
  assert split_joined_string('PythonCode') == ['Python', 'Code']
output: def split_joined_string(joined_string):
      for i in range(1, len(joined_string)):
          if joined_string[i].isupper():
              return [joined_string[:i], joined_string[i:]]