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([], 4) == []
  assert add_marks([78, 92], 0) == [78, 92]
  assert add_marks([100, 30, 50], -10) == [90, 20, 40]
  assert add_marks([45, 60, 75], 15) == [60, 75, 90]
output: def add_marks(marks, mark):
      return [x + mark for x in marks]