Add Gotenberg option generateDocumentOutline to $options array (#92)

* Add Gotenberg option generateDocumentOutline to $options array

* Add method_exists check before calling $option on the $chromium instance

* Move generateDocumentOutline to a separate block with a comment for minimum required versions to use the option

* Remove redundant != false check

* Add method_exists check for gotenberg-php < 2.10.0

src/Processor/Gotenberg.php

@@ -137,6 +137,12 @@ public function getPdfFromString(string $html, array $params = [], bool $returnF
             }
         }
 
+        // generateDocumentOutline is only available for gotenberg >= 8.14.0 and gotenberg-php >= v2.10.0
+        if (isset($params['generateDocumentOutline']) && $params['generateDocumentOutline']
+            && method_exists($chromium, 'generateDocumentOutline')) {
+            $chromium->generateDocumentOutline();
+        }
+
         $chromium->margins(
             $params['marginTop'] ?? 0.39,
             $params['marginBottom'] ?? 0.39,