next.js build: building contentlayer prior to TSC or adding more clear docs

When following the official Getting Started example for Next.js, the app fails to build on CI or any environemnt where `.contentlayer` doesn't exist already.

This appears to be because TSC runs _prior_ to contentlayer, which errors out.

I'm not sure if this can be changed at all (to run a Next plugin prior to the TSC step). That would seem like the ideal solution, but otherwise, would be great to update the documentation & examples to modify the build step

```json
"scripts": {
"build": "contentlayer && next build"
}
```

I'm happy to make a PR to help out, just wanted to check if this is indeed an issue that others experience or if I'm really missing something basic

Start with the official Getting Started example and its package.json build script, then reproduce the CI failure in an environment without .contentlayer. Check whether the documented build command needs Contentlayer to run first; done means the example builds successfully and the documentation reflects the required command or confirmed supported behavior.

Rédigé par le modèle d'indexation à partir du texte de l'issue.