start upgrading eslint

website/common/script/content/appearance/prefill.js

@@ -1,7 +1,7 @@
 import forOwn from 'lodash/forOwn';
 
 export default function prefillAppearances (obj) {
-  forOwn(obj, function prefillAppearance (value, key) {
+  forOwn(obj, (value, key) => {
     value.key = key;
     if (!value.price) {
       value.price = 0;