input: Write a function to join list items with a delimiter.
  assert join_list_items(["apple", "orange", "mango"], ", ") == "apple, orange, mango"
  assert join_list_items(["dog", "cat", "mouse"], " - ") == "dog - cat - mouse"
  assert join_list_items(["Python", "Java", "C++"], " | ") == "Python | Java | C++"
  assert join_list_items(["one"], ", ") == "one"
  assert join_list_items([], ", ") == ""
output: def join_list_items(items, delimiter):
      return delimiter.join(items)