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