Do not pack any moment.js locales except en.

nwb.config.js

@@ -1,3 +1,5 @@
+const { ContextReplacementPlugin } = require('webpack');
+
 module.exports = {
   type: 'react-app',
 
@@ -67,6 +69,10 @@ module.exports = {
     },
 
     extra: {
+      plugins: [
+        new ContextReplacementPlugin(/moment[/\\]locale$/, /en\.js/),
+      ],
+
       resolve: {
         extensions: [
           '.jsx',