Docs: add special warning to engine docs (#3979)

docs/backend/offline_engine_api.ipynb

@@ -18,10 +18,13 @@
     "- Non-streaming asynchronous generation\n",
     "- Streaming asynchronous generation\n",
     "\n",
+    "Additionally, you can easily build a custom server on top of the SGLang offline engine. A detailed example working in a python script can be found in [custom_server](https://github.com/sgl-project/sglang/blob/main/examples/runtime/engine/custom_server.py).\n",
     "\n",
-    "<span style=\"color:red\">**To launch the offline engine in your python scripts,** `__main__` **condition is necessary, since we use** `spawn` **mode to create subprocesses. Please refer to this** [simple example](https://github.com/sgl-project/sglang/blob/main/examples/runtime/engine/launch_engine.py) **for more details.**</span>\n",
+    "## SPECIAL WARNING!!!!\n",
     "\n",
-    "Additionally, you can easily build a custom server on top of the SGLang offline engine. A detailed example working in a python script can be found in [custom_server](https://github.com/sgl-project/sglang/blob/main/examples/runtime/engine/custom_server.py)."
+    "**To launch the offline engine in your python scripts,** `__main__` **condition is necessary, since we use** `spawn` **mode to create subprocesses. Please refer to this simple example**:\n",
+    "\n",
+    "https://github.com/sgl-project/sglang/blob/main/examples/runtime/engine/launch_engine.py"
    ]
   },
   {

docs/serve.sh

 make clean
 make html
-python3 -m http.server --d _build/html
+python3 -m http.server --d _build/html 8003