Fix internal linting setup and add missing headers (#1741)

packages/react-scripts/config/webpackDevServer.config.js

@@ -1,3 +1,15 @@
+// @remove-on-eject-begin
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+// @remove-on-eject-end
+'use strict';
+
 var config = require('./webpack.config.dev');
 var paths = require('./paths');