Prepare Release 0.13.20 (#1606)

Author: martineiber

src/OpenApi/Config/Spec.php

@@ -23,7 +23,7 @@
  * This class exists to document the public api
  */
 #[Info(
-    version: '0.12.18',
+    version: '0.13.20',
     description: 'API for Studio generated by OpenApi Generator via zircote/swagger-php',
     title: 'Studio Backend API'
 )]