[doc] Fold long code blocks to improve readability (#19926)

Signed-off-by: reidliu41 <reid201711@gmail.com>
Co-authored-by: reidliu41 <reid201711@gmail.com>

docs/getting_started/quickstart.md

@@ -147,20 +147,22 @@ curl http://localhost:8000/v1/completions \
 
 Since this server is compatible with OpenAI API, you can use it as a drop-in replacement for any applications using OpenAI API. For example, another way to query the server is via the `openai` Python package:
 
-```python
-from openai import OpenAI
+??? Code
 
-# Modify OpenAI's API key and API base to use vLLM's API server.
-openai_api_key = "EMPTY"
-openai_api_base = "http://localhost:8000/v1"
-client = OpenAI(
-    api_key=openai_api_key,
-    base_url=openai_api_base,
-)
-completion = client.completions.create(model="Qwen/Qwen2.5-1.5B-Instruct",
-                                      prompt="San Francisco is a")
-print("Completion result:", completion)
-```
+    ```python
+    from openai import OpenAI
+
+    # Modify OpenAI's API key and API base to use vLLM's API server.
+    openai_api_key = "EMPTY"
+    openai_api_base = "http://localhost:8000/v1"
+    client = OpenAI(
+        api_key=openai_api_key,
+        base_url=openai_api_base,
+    )
+    completion = client.completions.create(model="Qwen/Qwen2.5-1.5B-Instruct",
+                                        prompt="San Francisco is a")
+    print("Completion result:", completion)
+    ```
 
 A more detailed client example can be found here: <gh-file:examples/online_serving/openai_completion_client.py>
 
@@ -184,26 +186,28 @@ curl http://localhost:8000/v1/chat/completions \
 
 Alternatively, you can use the `openai` Python package:
 
-```python
-from openai import OpenAI
-# Set OpenAI's API key and API base to use vLLM's API server.
-openai_api_key = "EMPTY"
-openai_api_base = "http://localhost:8000/v1"
+??? Code
 
-client = OpenAI(
-    api_key=openai_api_key,
-    base_url=openai_api_base,
-)
+    ```python
+    from openai import OpenAI
+    # Set OpenAI's API key and API base to use vLLM's API server.
+    openai_api_key = "EMPTY"
+    openai_api_base = "http://localhost:8000/v1"
 
-chat_response = client.chat.completions.create(
-    model="Qwen/Qwen2.5-1.5B-Instruct",
-    messages=[
-        {"role": "system", "content": "You are a helpful assistant."},
-        {"role": "user", "content": "Tell me a joke."},
-    ]
-)
-print("Chat response:", chat_response)
-```
+    client = OpenAI(
+        api_key=openai_api_key,
+        base_url=openai_api_base,
+    )
+
+    chat_response = client.chat.completions.create(
+        model="Qwen/Qwen2.5-1.5B-Instruct",
+        messages=[
+            {"role": "system", "content": "You are a helpful assistant."},
+            {"role": "user", "content": "Tell me a joke."},
+        ]
+    )
+    print("Chat response:", chat_response)
+    ```
 
 ## On Attention Backends