turn on ascii_only for issue with emoji and regex (facebook#2596)

Author: viankakrisna

Diff for: packages/react-scripts/config/webpack.config.prod.js

@@ -290,6 +290,9 @@ module.exports = {
       },
       output: {
         comments: false,
+        // Turned on because emoji and regex is not minified properly using default
+        // https://github.com/facebookincubator/create-react-app/issues/2488
+        ascii_only: true,
       },
       sourceMap: true,
     }),