input: Write a function to add a given mark to each value in a marks list. The function should be called add_marks and take two parameters: marks (a list) and mark (an integer). The function should return a new list with the updated marks.
  assert add_marks([87, 56, 99, 54], 4)==[91, 60, 103, 58]
  assert add_marks([10, 20, 30], 5)==[15, 25, 35]
  assert add_marks([78, 92, 66], 0)==[78, 92, 66]
  assert add_marks([], 3)==[]
output: def add_marks(marks, mark):
      return [x + mark for x in marks]