make webpack middleware into boot scripts

server/boot/dev/webpack-hmr.js

@@ -0,0 +1,12 @@
+const webpackHotMiddleware = require('webpack-hot-middleware');
+const webpack = require('../../helpers/webpack');
+
+const isProduction = (process.env.NODE_ENV === 'production');
+
+module.exports = (app) => {
+  if (isProduction) return;
+
+  const middleware = webpackHotMiddleware(webpack.compiler);
+
+  app.use(middleware);
+};