docs: update react preamble instruction

docs/guide/backend-integration.md

@@ -35,11 +35,11 @@ If you want to serve the HTML using a traditional backend (e.g. Rails, Laravel)
 
    Also make sure the server is configured to serve static assets in the Vite working directory, otherwise assets such as images won't be loaded properly.
 
-   Note if you are using React with `@vitejs/plugin-react-refresh`, you'll also need to add this, since the plugin is not able to modify the HTML you are serving:
+   Note if you are using React with `@vitejs/plugin-react-refresh`, you'll also need to add this before the above scripts, since the plugin is not able to modify the HTML you are serving:
 
    ```html
    <script type="module">
-     import RefreshRuntime from "/@react-refresh"
+     import RefreshRuntime from "http://localhost:3000/@react-refresh"
      RefreshRuntime.injectIntoGlobalHook(window) window.$RefreshReg$ = () => {}
      window.$RefreshSig$ = () => (type) => type
      window.__vite_plugin_react_preamble_installed__ = true