[lv.1] 행렬의 덧셈

https://school.programmers.co.kr/learn/courses/30/lessons/12950

function solution(arr1, arr2) {
  let arr = [];
  
    for (let i=0; i<arr1.length; i++) {
      let answer = [];
      for (let j=0; j<arr1[i].length; j++) {
        answer.push(arr1[i][j] + arr2[i][j])
      }
    	arr.push(answer);
    }
  
   return arr
}