Add Next.js App Router Demo to PostHog Playground

[mavdotso]

Hey team!

I was integrating PostHog into my Next.js app and couldn't find an app-router demo, so I created one using docs and this tutorial.

With this PR, I'm adding a new demo project to the PostHog playground and including examples of client- and server-side event tracking.

Changes

• Added a new directory nextjs-app to the playground
• Implemented sample page examaples for client-side and server-side event tracking
• Integrated PostHog provider and event tracking components for AppRouter

Features

1. Client-side event tracking using the usePostHog hook
2. Server-side event tracking using the PostHog Node.js library
3. Integration of PostHog with the latest Next.js App Router
4. Sample pages demonstrating client and server-side event tracking

[vercel]

@mavdotso is attempting to deploy a commit to the PostHog Team on Vercel.

A member of the Team first needs to authorize it.

[posthog-bot]

This PR hasn't seen activity in a week! Should it be merged, closed, or further worked on? If you want to keep it open, post a comment or remove the stale label – otherwise this will be closed in another week.

[posthog-bot]

This PR was closed due to lack of activity. Feel free to reopen if it's still relevant.