Write a function that takes three arguments (x, y, z) and returns an array containing x subarrays (e.g. [[], [], []]), each containing y number of item z.
x Number of subarrays contained within the main array.y Number of items contained within each subarray.z Item contained within each subarray.matrix(3, 2, 3) ➞ [[3, 3], [3, 3], [3, 3]]
matrix(2, 1, "innokodakademija") ➞ [["innokodakademija"], ["innokodakademija"]]
matrix(3, 2, 0) ➞ [[0, 0], [0, 0], [0, 0]]