input: Write a function 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([100, 200, 300], 0)==[100, 200, 300]
  assert add_marks([1, 2, 3], -1)==[0, 1, 2]
  assert add_marks([], 10)==[]
  assert add_marks([5], -5)==[0]
output: def add_marks(marks, mark):
      return [x + mark for x in marks]