Fix error overlay 'Object.assign' issue in IE by including polyfills before webpack client (facebook#3046)

Author: tharakawj

packages/react-scripts/config/webpack.config.dev.js

@@ -67,7 +67,8 @@ module.exports = {
   // The first two entry points enable "hot" CSS and auto-refreshes for JS.
   entry: {
     [mainEntry]: [
-      // Include an alternative client for WebpackDevServer. A client's job is to
+      // We ship a few polyfills by default:
+      require.resolve('./polyfills'),// Include an alternative client for WebpackDevServer. A client's job is to
       // connect to WebpackDevServer by a socket and get notified about changes.
       // When you save a file, the client will either apply hot updates (in case
       // of CSS changes), or refresh the page (in case of JS changes). When you
@@ -78,10 +79,6 @@ module.exports = {
       // require.resolve('webpack-dev-server/client') + '?/',
       // require.resolve('webpack/hot/dev-server'),
       require.resolve('react-dev-utils/webpackHotDevClient'),
-      // We ship a few polyfills by default:
-      require.resolve('./polyfills'),
-      // Errors should be considered fatal in development
-      require.resolve('react-error-overlay'),
       // Finally, this is your app's code:
       paths.appIndexJs,
       // We include the app code last so that if there is a runtime error during