Added module property to webpack config.

webpack.config.js.diff

   },
   devServer: {
     contentBase: path.join(__dirname, "public"),
     https: true,
   },
+  module: {
+    rules: [
+      {
+        test : /\.js/,
+        include: path.resolve(__dirname, 'src/'),
+        use: ['babel-loader'],
+      },
+    ],
+  },
 };