add dev task that writes output to disk

webpack.dev-write.js

@@ -0,0 +1,9 @@
+/* global require */
+const merge = require('webpack-merge');
+const WriteFilePlugin = require('write-file-webpack-plugin');
+
+module.exports = merge.smart(require('./webpack.dev.js'), {
+  plugins: [
+    new WriteFilePlugin(),
+  ],
+});