adding preview screeshot

Author: Rolando Santamaria Maso

README.md

@@ -18,4 +18,6 @@ const catalog = [{
 ```bash
 npm start
 ```
-> Swagger Documentation catalog is available at http://0.0.0.0:3000
+> Swagger Documentation catalog is available at http://0.0.0.0:3000
+
+![Example Preview](./swagger-api-browser.png)