🚀 Feature: Support Next.js as a build tool (opt-in Block)

### Feature Request Checklist

- [x] I have pulled the latest `main` branch of the repository.
- [x] I have [searched for related issues](https://github.com/JoshuaKGoldberg/create-typescript-app/issues?q=is%3Aissue) and found none that matched my issue.

### Overview

Similar to #1917 and the other alternate builders mentioned in https://github.com/JoshuaKGoldberg/create-typescript-app/issues/1917#issuecomment-2779580434: some projects built on CTA use [Next.js](https://nextjs.org) as a builder. I'd like to have an opt-in `blockNextJs` Block (or some similar name, I'm not sold on the capitalization...) provided that provides the basic building blocks of a CTA-managed `next.config.js` and `package.json` scripts.

### Additional Info

For reference of a CTA & Next.js repository, see: https://github.com/JoshuaKGoldberg/tidelift-me-up-site

🎁