input: Write a function to sort a list of strings based on their length. The function should return the sorted list. If the input list is empty, the function should return an empty list.
  assert sort_strings_by_length(["Hello","World!","Good","Morning"])==["Good","Hello","World!","Morning"]
  assert sort_strings_by_length([])==[]
output: def sort_strings_by_length(strings):
      return sorted(strings, key=len)