Add Next.js demo

[sequba]

Description

This example should demonstrate running HF server-side and should satisfy the requirements of task #972

Next.js is recommended by official React docs: https://react.dev/learn/start-a-new-react-project

Use TDD.

Links

#972

Type of issue

• [ ] Missing documentation
• [ ] Error in the documentation
• [x] Request for a demo
• [ ] Request for a tutorial, guide etc.
• [ ] Other issues, suggestions or ideas