input: Write a function add_marks(marks, mark) 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([95, 78, 88], 3)==[98, 81, 91]
  assert add_marks([100, 200], 0)==[100, 200]
  assert add_marks([], 5)==[]
  assert add_marks([45, 50, 55], -5)==[40, 45, 50]
output: def add_marks(marks, mark):
      return [x + mark for x in marks]