feat: help for additional properties in LlmGenerationClient config

Author: Haleshot

rust/cocoindex/src/llm/openai.rs

@@ -162,6 +162,7 @@ impl LlmGenerationClient for Client {
             supports_format: false,
             extract_descriptions: false,
             top_level_must_be_object: true,
+            supports_additional_properties: true,
         }
     }
 }