input: Write a python function to find the length of the longest increasing subarray.
  assert longest_increasing_subarray([1, 3, -2, 5, 8, -3, 4, 6]) == 3
  assert longest_increasing_subarray([10, 20, 30, 40, 50]) == 5
  assert longest_increasing_subarray([5, 4, 3, 2, 1]) == 1
  assert longest_increasing_subarray([1, 2, 2, 3, 4, 1, 5, 6]) == 4
output: def longest_increasing_subarray(arr):
      if not arr:
          return 0
  
      max_len = 1
      current_len = 1
  
      for i in range(1, arr.length):
          if arr[i] > arr[i - 1]:
              current_len += 1
              max_len = max(max_len, current_len)
          else:
              current_len = 1
  
      return max_len