fix: early return 추가

Author: sujeong-dev

valid-anagram/sujeong-dev.js

@@ -4,6 +4,8 @@
  * @return {boolean}
  */
 var isAnagram = function (s, t) {
+  if (s.length !== t.length) return false;
+  
   const frequencyMap = new Map();
 
   for (const x of s) {