Add readme comment

README.md

@@ -54,6 +54,7 @@ Some things to try:
       - Clicking on `Open in Browser` in the notification telling you: `Your service running on port 3000 is available`.
       - Clicking the globe icon in the 'Ports' view. The 'Ports' view gives you an organized table of your forwarded ports, and you can access it with the command **Ports: Focus on Ports View**.
    - Notice port 3000 in the 'Ports' view is labeled "Hello Remote World." In `devcontainer.json`, you can set `"portsAttributes"`, such as a label for your forwarded ports and the action to be taken when the port is autoforwarded. 
+      - If we didn't know the port was 3000, we could've used a regex instead of "3000" in the `"portsAttributes"`, such as ".+/server.js".
 
    > **Note:** In Remote - Containers, you can access your app at `http://localhost:3000` in a local browser. But in a browser-based Codespace, you must click the link from the notification or the `Ports` view so that the service handles port forwarding in the browser and generates the correct URL.