添加（0027.移除元素.md）：增加 typescript 版本

problems/0027.移除元素.md

@@ -197,7 +197,23 @@ var removeElement = (nums, val) => {
 };
 ```
 
+TypeScript：
+
+```typescript
+function removeElement(nums: number[], val: number): number {
+    let slowIndex: number = 0, fastIndex: number = 0;
+    while (fastIndex < nums.length) {
+        if (nums[fastIndex] !== val) {
+            nums[slowIndex++] = nums[fastIndex];
+        }
+        fastIndex++;
+    }
+    return slowIndex;
+};
+```
+
 Ruby:
+
 ```ruby
 def remove_element(nums, val)
     i = 0