MDL-66265 javascript: Add jshint ignore for ES6 files in root dir

.eslintrc

@@ -203,7 +203,7 @@
       }
     },
     {
-      files: ["**/amd/src/*.js"],
+      files: ["**/amd/src/*.js", "*.js"],
       // Check AMD with some slightly stricter rules.
       rules: {
         'no-unused-vars': 'error',

.jshintignore

@@ -1 +1,2 @@
 **/amd/**
+/*.js

Gruntfile.js

@@ -24,6 +24,7 @@
  * Grunt configuration
  */
 
+/* eslint-env node */
 module.exports = function(grunt) {
     var path = require('path'),
         tasks = {},