[Suggestion] Add Next.js 14/15 (App Router) tutorials to the JS/TS section

Hi team! Since the React ecosystem has heavily shifted towards the Next.js App Router, it would be awesome to see some updated full-stack project tutorials using Next.js 14/15 in the JavaScript/TypeScript section. Currently, many tutorials focus on older React versions. Let me know if you're open to this, and I can hunt down some high-quality, free tutorials and open a PR!