Add chat image upload support

README.md

@@ -69,6 +69,39 @@ with ChatClient(api_key="fastgpt-xxxxx") as client:
     )
 ```
 
+### Chat with an Image
+
+Upload the image to FastGPT's chat file storage first, then reference the returned URL in a chat message.
+
+```python
+from fastgpt_client import ChatClient
+
+app_id = "your-app-id"
+chat_id = "my_conversation_123"
+
+with ChatClient(api_key="fastgpt-xxxxx", base_url="http://localhost:3000") as client:
+    image = client.upload_chat_image(
+        appId=app_id,
+        chatId=chat_id,
+        file_path="example.png",
+    )
+
+    response = client.create_chat_completion(
+        chatId=chat_id,
+        messages=[
+            {
+                "role": "user",
+                "content": [
+                    {"type": "text", "text": "Please describe this image."},
+                    {"type": "image_url", "image_url": {"url": image["url"]}},
+                ],
+            }
+        ],
+    )
+
+    print(response.json()["choices"][0]["message"]["content"])
+```
+
 ### Using Variables
 
 ```python