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 and return the modified list.
  assert add_marks([87, 56, 99, 54], 4) == [91, 60, 103, 58]
  assert add_marks([30, 45, 60], 5) == [35, 50, 65]
  assert add_marks([80, 81, 82], 0) == [80, 81, 82]
  assert add_marks([], 10) == []
output: def add_marks(marks, mark):
      return [x + mark for x in marks]