Create a function that takes two numbers as arguments (num, length) and returns a list of multiples of num until the list length reaches length.
list_of_multiples(7, 5) ➞ [7, 14, 21, 28, 35]
list_of_multiples(12, 10) ➞ [12, 24, 36, 48, 60, 72, 84, 96, 108, 120]
list_of_multiples(17, 6) ➞ [17, 34, 51, 68, 85, 102]
Notice that num is also included in the returned list.