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([10, 20, 30], 5)==[15, 25, 35]
  assert add_marks([90, 80, 70], -5)==[85, 75, 65]
  assert add_marks([], 10)==[]
  assert add_marks([45], 0)==[45]
output: def add_marks(marks, mark):
      return [x + mark for x in marks]