input: Write a function called add_marks which takes two parameters: marks(a list) and mark(an integer). The function should add the mark to each value in the marks list.
  assert add_marks([87, 56, 99, 54], 4)==[91, 60, 103, 58]
  assert add_marks([75, 80, 85], 2)==[77, 82, 87]
  assert add_marks([60, 65, 70], 0)==[60, 65, 70]
  assert add_marks([10, 20, 30], -5)==[5, 15, 25]
  assert add_marks([], 3)==[]
output: def add_marks(marks, mark):
      return [x + mark for x in marks]