Added root route that returns server status message

app/server.py

@@ -15,6 +15,11 @@ app = FastAPI(
   description="A simple api server using Langchain's Runnable interfaces",
 )
 
+@app.get("/")
+async def root():
+    # return json response
+    return {"message": "LangChain Server is running"}
+
 add_routes(
     path    = "/openai",
     app     = app,