Sort secondary diagonals for a 2D matrix.\nSimilar to this question: [1329. Sort the Matrix Diagonally](https://leetcode.com/problems/sort-the-matrix-diagonally/). However, the sorting diagonal is the secondary one. I could not solve it as I did not know which way to nest the loop.

Sort secondary diagonals for a 2D matrix.\nSimilar to this question: 1329. Sort the Matrix Diagonally. However, the sorting diagonal is the secondary one. I cou