Update README.md

Author: RyanDaDeng

README.md

@@ -33,7 +33,7 @@ $ composer require ryandeng/googlerecaptcha "^0.1.3"
 
 If your Laravel framework version <= 5.4, please register the service provider in your config file: /config/app.php, otherwise please go to step 3.
 
-```
+``` php
 RyanDeng\GoogleReCaptcha\Providers\GoogleReCaptchaV3ServiceProvider::class
 ```