next.js

eecf90c0 - updated the environment variables examples to utilize the App router (#70392)

updated the environment variables examples to utilize the App router (#70392) This PR updates the `environment-variables` example to use the App Router. Here are the changes that have been made: - Created an `app` folder and added `page.tsx` file. - Added `layout.tsx` file - Updated the `readme.md` file. - Updated the `package.json` file. cc : @samcx --------- Co-authored-by: samcx <sam@vercel.com>