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

Comienza con el ejemplo oficial de Getting Started y su script de build de package.json, y luego reproduce el fallo de CI en un entorno sin .contentlayer. Comprueba si el comando de build documentado necesita ejecutar primero Contentlayer; el trabajo estará terminado cuando el ejemplo se compile correctamente y la documentación refleje el comando necesario o el comportamiento compatible confirmado.

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