Problem
HackerRank detailed problem description can be found here
[https://www.hackerrank.com/challenges/30-2d-arrays/problem].
Inputs & Outputs
/*
input {array} arr - 6x6 2d array
output {number} - maximum hourglass sum
*/
Test Case
let arr = [
[1, 1, 1, 0, 0, 0],
[0, 1, 0, 0, 0, 0],
[1, 1,