input: Write a python function to perform a linear search in a list.
  assert linearSearch([1, 2, 3, 4, 5], 3) == 2
  assert linearSearch([10, 20, 30, 40, 50], 50) == 4
  assert linearSearch([7, 8, 9, 10, 11], 6) == -1
output: def linearSearch(lst, target):
      for index, value in enumerate(lst):
          if value == target:
              return index
      return -1