input: Write a python function to sort a list of numbers using selection sort algorithm.
  assert sort_numbers([2, 5, 1, 3, 8, 4]) == [1, 2, 3, 4, 5, 8]
  assert sort_numbers([10, 3, 15, 7, 8, 23, 74, 18]) == [3, 7, 8, 10, 15, 18, 23, 74]
  assert sort_numbers([5, 4, 3, 2, 1]) == [1, 2, 3, 4, 5]
output: def sort_numbers(arr):
      n = len(arr)
      for i in range(n):
          min_idx = i
          for j in range(i+1, n):
              if arr[j] < arr[min_idx]:
                  min_idx = j
          arr[i], arr[min_idx] = arr[min_idx], arr[i]
      return arr