input: Write a function to sort two arrays of strings and concatenate them.
  assert sort_str_arr(["zebra", "apple", "carrot"], ["banana", "elephant", "cat"]) == ["apple", "banana", "carrot", "cat", "elephant", "zebra"]
  assert sort_str_arr(["dog", "cat", "bird"], ["zebra", "lion", "tiger"]) == ["bird", "cat", "dog", "lion", "tiger", "zebra"]
  assert sort_str_arr(["mango", "apple"], ["banana", "cherry"]) == ["apple", "banana", "cherry", "mango"]
output: def sort_str_arr(arr1, arr2):
      combined = arr1 + arr2
      combined.sort()
      return combined