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([], 7) == []
  assert add_marks([1, 2, 3, 4, 5], 0) == [1, 2, 3, 4, 5]
output: def add_marks(marks, mark):
      return [x + mark for x in marks]