Add header comment

packages/react-error-overlay/build.js

@@ -1,3 +1,13 @@
+/**
+ * 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.
+ */
+'use strict';
+
 const webpack = require('webpack');
 const chalk = require('chalk');
 const webpackConfig = require('./webpack.config.js');

packages/react-error-overlay/src/iframeScript.js

@@ -6,6 +6,7 @@
  * 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.
  */
+
 import './utils/pollyfills.js';
 import React from 'react';
 import ReactDOM from 'react-dom';

packages/react-error-overlay/webpack.config.iframe.js

@@ -1,5 +1,14 @@
-var path = require('path');
-var webpack = require('webpack');
+/**
+ * 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.
+ */
+'use strict';
+
+const path = require('path');
 
 module.exports = {
   devtool: 'cheap-module-source-map',

packages/react-error-overlay/webpack.config.js

@@ -1,5 +1,14 @@
-var path = require('path');
-var webpack = require('webpack');
+/**
+ * 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.
+ */
+'use strict';
+
+const path = require('path');
 
 module.exports = {
   devtool: 'cheap-module-source-map',