Bump webpacker from 3.5.5 to 4.0.2 (#10277)

Bumps [webpacker](https://github.com/rails/webpacker) from 3.5.5 to 4.0.2.
- [Release notes](https://github.com/rails/webpacker/releases)
- [Changelog](https://github.com/rails/webpacker/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rails/webpacker/compare/v3.5.5...v4.0.2)

Signed-off-by: dependabot[bot] <support@dependabot.com>
Co-authored-by: Yamagishi Kazutoshi <ykzts@desire.sh>

config/webpack/development.js

@@ -1,12 +1,10 @@
 // Note: You must restart bin/webpack-dev-server for changes to take effect
 
 const merge = require('webpack-merge');
-const sharedConfig = require('./shared.js');
-const { settings, output } = require('./configuration.js');
+const sharedConfig = require('./shared');
+const { settings, output } = require('./configuration');
 
-const watchOptions = {
-  ignored: /node_modules/,
-};
+const watchOptions = {};
 
 if (process.env.VAGRANT) {
   // If we are in Vagrant, we can't rely on inotify to update us with changed
@@ -17,7 +15,7 @@ if (process.env.VAGRANT) {
 
 module.exports = merge(sharedConfig, {
   mode: 'development',
-
+  cache: true,
   devtool: 'cheap-module-eval-source-map',
 
   stats: {
@@ -30,15 +28,33 @@ module.exports = merge(sharedConfig, {
 
   devServer: {
     clientLogLevel: 'none',
-    https: settings.dev_server.https,
+    compress: settings.dev_server.compress,
+    quiet: settings.dev_server.quiet,
+    disableHostCheck: settings.dev_server.disable_host_check,
     host: settings.dev_server.host,
     port: settings.dev_server.port,
+    https: settings.dev_server.https,
+    hot: settings.dev_server.hmr,
     contentBase: output.path,
+    inline: settings.dev_server.inline,
+    useLocalIp: settings.dev_server.use_local_ip,
+    public: settings.dev_server.public,
     publicPath: output.publicPath,
-    compress: true,
-    headers: { 'Access-Control-Allow-Origin': '*' },
-    historyApiFallback: true,
-    disableHostCheck: true,
-    watchOptions: watchOptions,
+    historyApiFallback: {
+      disableDotRule: true,
+    },
+    headers: settings.dev_server.headers,
+    overlay: settings.dev_server.overlay,
+    stats: {
+      entrypoints: false,
+      errorDetails: false,
+      modules: false,
+      moduleTrace: false,
+    },
+    watchOptions: Object.assign(
+      {},
+      settings.dev_server.watch_options,
+      watchOptions
+    ),
   },
 });