fix(nuxt): include external layers in tsconfig.json scope

[agenordebriat]

🔗 Linked issue

#21877

❓ Type of change

• 📖 Documentation (updates to the documentation, readme or JSdoc annotations)
• 🐞 Bug fix (a non-breaking change that fixes an issue)
• 👌 Enhancement (improving an existing functionality like performance)
• ✨ New feature (a non-breaking change that adds functionality)
• 🧹 Chore (updates to the build process or auxiliary tools and libraries)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

Not sure which type(s) apply.

📚 Description

Volar 1.8.2 introduced a breaking change regarding the way it handles tsconfig.

Until this PR, we needed to manually add our layer(s) paths to the include section, that'd override the default one, on our project tsconfig to get support for things like autocompletion. Something like:

"include": [
    ".nuxt/nuxt.d.ts",
    "**/*",
    "<path to layer files>"
],

What this PR does is check nuxt.options._layers for paths that are different than nuxt.options.rootDir and add them, with a trailing **/* to the include array, next to ./nuxt.d.ts and all the other ones.

There's probably a better way to do it, but it works for now.

📝 Checklist

• I have linked an issue or discussion.
• I have updated the documentation accordingly.

I don't think documentation should mention it, as it's transparent for the user like the rest of the tsconfig file.