add initial files

.erb/scripts/check-node-env.js

@@ -0,0 +1,16 @@
+import chalk from 'chalk';
+
+export default function checkNodeEnv(expectedEnv) {
+  if (!expectedEnv) {
+    throw new Error('"expectedEnv" not set');
+  }
+
+  if (process.env.NODE_ENV !== expectedEnv) {
+    console.log(
+      chalk.whiteBright.bgRed.bold(
+        `"process.env.NODE_ENV" must be "${expectedEnv}" to use this webpack config`
+      )
+    );
+    process.exit(2);
+  }
+}