docs: add link to api references for create_react_agent (#759)

examples/create-react-agent.ipynb

@@ -131,6 +131,14 @@
     "### Define the graph"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "id": "2a2da4e4",
+   "metadata": {},
+   "source": [
+    "We're going to use a prebuilt implementation of ReAct agent included with `langgraph` library - [`create_react_agent`](https://langchain-ai.github.io/langgraph/reference/prebuilt/#create_react_agent)"
+   ]
+  },
   {
    "cell_type": "code",
    "execution_count": 4,