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], 0) == [10, 20, 30]
  assert add_marks([], 5) == []
  assert add_marks([1, 1, 1], 2) == [3, 3, 3]
output: def add_marks(marks, mark):
      return [x + mark for x in marks]