Create a function to multiply all of the values in an array by the amount of values in the given array.
multiplyByLength([2, 3, 1, 0]) ➞ [8, 12, 4, 0]
multiplyByLength([4, 1, 1]) ➞ ([12, 3, 3])
multiplyByLength([1, 0, 3, 3, 7, 2, 1]) ➞ [7, 0, 21, 21, 49, 14, 7]
multiplyByLength([0]) ➞ ([0])