添加（0090.子集II.md）：增加typescript版本

problems/0090.子集II.md

@@ -319,6 +319,28 @@ var subsetsWithDup = function(nums) {
 
 ```
 
+### TypeScript
+
+```typescript
+function subsetsWithDup(nums: number[]): number[][] {
+    nums.sort((a, b) => a - b);
+    const resArr: number[][] = [];
+    backTraking(nums, 0, []);
+    return resArr;
+    function backTraking(nums: number[], startIndex: number, route: number[]): void {
+        resArr.push(route.slice());
+        let length: number = nums.length;
+        if (startIndex === length) return;
+        for (let i = startIndex; i < length; i++) {
+            if (i > startIndex && nums[i] === nums[i - 1]) continue;
+            route.push(nums[i]);
+            backTraking(nums, i + 1, route);
+            route.pop();
+        }
+    }
+};
+```
+
 ### C 
 
 ```c
@@ -388,7 +410,7 @@ int** subsetsWithDup(int* nums, int numsSize, int* returnSize, int** returnColum
 }
 ```
 
-## Swift
+### Swift
 
 ```swift
 func subsetsWithDup(_ nums: [Int]) -> [[Int]] {