input: Write a python function to convert a string into a shell command format.
  assert string_to_shell_command("ls -la") == 'ls "-la" '
  assert string_to_shell_command("echo Hello World") == 'echo "Hello" "World" '
  assert string_to_shell_command("mkdir new_folder") == 'mkdir "new_folder" '
output: def string_to_shell_command(s):
      return ' '.join(f'"{word}"' for word in s.split()) + ' '