-------- | PUSH | -------- 1. Append the data to the array emulating the functionality of a stack.   TIME COMPLEXITY: O(1)
------- | POP | ------- 1. Truncate the last element of the array and return it.   TIME COMPLEXITY: O(1)
-------- | PEEK | -------- 1. Return the element last added to the array without removing it.   TIME COMPLEXITY: O(1)