Update readme

Author: wilsenhc

README.md

@@ -34,6 +34,17 @@ php artisan vendor:publish --provider="Wilsenhc\RifValidation\RifValidationServi
 
 This validation rule will pass if the RIF value passed in the request is valid.
 
+```php
+// in a `FormRequest`
+public function rules()
+{
+    return [
+        'rif' => 'required|rif',
+    ];
+}
+```
+You can also import the `Rif` Rule class and use it instead
+
 ```php
 // in a `FormRequest`