Fix typo

Author: Tomek Wiszniewski

README.md

@@ -682,13 +682,13 @@ Other Style Guides
     ));
 
     // bad
-    [1, 2, 3].reduce(x => {
+    [1, 2, 3].map(x => {
       const y = x + 1;
       return x * y;
     });
 
     // good
-    [1, 2, 3].reduce((x) => {
+    [1, 2, 3].map((x) => {
       const y = x + 1;
       return x * y;
     });