Add custom data to the JSON file

When writing the hook file, the config-custom-data was missing.
Issue: #278

Author: sebastianfeldmann

src/Config.php

@@ -408,6 +408,9 @@ public function getJsonData(): array
         if (!empty($this->plugins)) {
             $data['config']['plugins'] = $this->getPluginsJsonData();
         }
+        if (!empty($this->custom)) {
+            $data['config']['custom'] = $this->custom;
+        }
         foreach (Hooks::getValidHooks() as $hook => $value) {
             $data[$hook] = $this->hooks[$hook]->getJsonData();
         }