feat: add ts solution to lc problem: No.1572 (doocs#1426)

Author: thinkasany

solution/1500-1599/1572.Matrix Diagonal Sum/README.md

@@ -133,6 +133,18 @@ func diagonalSum(mat [][]int) (ans int) {
 
 ### **TypeScript**
 
+```ts
+function diagonalSum(mat: number[][]): number {
+    let ans = 0;
+    const n = mat.length;
+    for (let i = 0; i < n; ++i) {
+        const j = n - i - 1;
+        ans += mat[i][i] + (i === j ? 0 : mat[i][j]);
+    }
+    return ans;
+}
+```
+
 ```ts
 function diagonalSum(mat: number[][]): number {
     const n = mat.length;

solution/1500-1599/1572.Matrix Diagonal Sum/README_EN.md

@@ -113,6 +113,18 @@ func diagonalSum(mat [][]int) (ans int) {
 
 ### **TypeScript**
 
+```ts
+function diagonalSum(mat: number[][]): number {
+    let ans = 0;
+    const n = mat.length;
+    for (let i = 0; i < n; ++i) {
+        const j = n - i - 1;
+        ans += mat[i][i] + (i === j ? 0 : mat[i][j]);
+    }
+    return ans;
+}
+```
+
 ```ts
 function diagonalSum(mat: number[][]): number {
     const n = mat.length;