Added manifest building.

webpack/webpack.prod.js

@@ -1,6 +1,11 @@
 const merge = require('webpack-merge');
 const common = require('./webpack.common.js');
 
-module.exports = merge(common, {
-    mode: 'production'
-});
+module.exports = env => {
+    let mode = "production";
+    env.mode = mode;
+
+    return merge(common(env), {
+        mode
+    });
+};