添加（0209.长度最小的子数组.md）：增加typescript版本

problems/0209.长度最小的子数组.md

@@ -214,6 +214,28 @@ var minSubArrayLen = function(target, nums) {
 };
 ```
 
+Typescript：
+
+```typescript
+function minSubArrayLen(target: number, nums: number[]): number {
+    let left: number = 0, right: number = 0;
+    let res: number = nums.length + 1;
+    let sum: number = 0;
+    while (right < nums.length) {
+        sum += nums[right];
+        if (sum >= target) {
+            // 不断移动左指针，直到不能再缩小为止
+            while (sum - nums[left] >= target) {
+                sum -= nums[left++];
+            }
+            res = Math.min(res, right - left + 1);
+        }
+        right++;
+    }
+    return res === nums.length + 1 ? 0 : res;
+};
+```
+
 Swift:
 
 ```swift