Update README.md

Author: yanglbme

solution/0900-0999/0921.Minimum Add to Make Parentheses Valid/README.md

@@ -306,12 +306,15 @@ function minAddToMakeValid(s: string): number {
 #### JavaScript
 
 ```js
-function minAddToMakeValid(s: string): number {
+/**
+ * @param {string} s
+ * @return {number}
+ */
+var minAddToMakeValid = function (s) {
     const l = s.length;
     s = s.replace('()', '');
-
     return s.length === l ? l : minAddToMakeValid(s);
-}
+};
 ```
 
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