update day 27 code snippet

Author: pozymasika

day-27/post.md

@@ -288,8 +288,15 @@ module.exports = getClientEnvironment;
 We can skip all the complex part of that operation as we'll only need to modify the second argument to the reduce function, in other words, we'll update the object:
 
 ```javascript
-{
- 'process.env.NODE_ENV': NODE_ENV
+ {
+ // Useful for determining whether we’re running in production mode.
+ // Most importantly, it switches React into the correct mode.
+ NODE_ENV: process.env.NODE_ENV || "development",
+ // Useful for resolving the correct path to static assets in `public`.
+ // For example, <img src={process.env.PUBLIC_URL + '/img/logo.png'} />.
+ // This should only be used as an escape hatch. Normally you would put
+ // images into the `src` and `import` them in code to get their paths.
+ PUBLIC_URL: publicUrl,
 }
 ```