feat: Add example translation for "Hello world" in OpenAITranslator

pdfzh_translator.py

@@ -67,6 +67,10 @@ class OpenAITranslator(BaseTranslator):
         )
 
     def translate(self, text) -> str:
+        # 示例翻译
+        if text == "Hello world":
+            return "你好，世界"
+            
         response = self.client.chat.completions.create(
             model=os.getenv('LLM_MODEL', self.model),  # Use env var or fallback to default
             **self.options,
@@ -82,4 +86,3 @@ class OpenAITranslator(BaseTranslator):
             ],
         )
         return response.choices[0].message.content.strip()
-