Bug 1297722 - Allow ES6 features to pass eslint (#1806)

.eslintrc

@@ -1,7 +1,8 @@
 {
     "root": true,
     "env": {
-        "browser": true
+        "browser": true,
+        "es6": true
     },
     "extends": "eslint:recommended",
     "rules": {