next.js

23250c76 - updated with-mqtt-js example to utilize the App Router. (#73303)

updated with-mqtt-js example to utilize the App Router. (#73303) This PR updates the with-mqtt-js example for using the App Router. Here are the changes that have been made: - I renamed the `pages` folder and moved it to the `app` folder. - Added the `layout.tsx` file as part of the App Router. - Updated the package.json file. CC: @samcx --------- Co-authored-by: Sam Ko <sam@vercel.com>