Improve welcome page experience

[atinux]

Starting npx nuxt dev in an empty project (with only a package.json and node_modules) should work and display the tutorial.

✅ This is working perfectly

Then, we create an app.vue file, nothings happens, we stay on the tutorial, the VFS is updated though (http://localhost:4000/_vfs/%2FUsers%2Fatinux%2FProjects%2Fnuxt%2Fframework%2Fexample%2F.nuxt%2Fapp.mjs)

Same we having an app.vue when running the development server and removing it.

One easy solution would be to restart the whole Nuxt dev server since the creation of these file should happen only at the beginning of the project.

[pi0]

Restarting can be a quick fix indeed and a fresh project has no files so restart is almost instant. I've moved it to #11910

Also in starter templates and CSB, we usually have placeholder app.vue and/or pages/index.vue which we could add a special comment to render welcome page like above until user adds first line of code.

app.vue:

<template>
   <!-- remove this line -->
</template>

As a bonus, we can add a "Get Started" button to the welcome page that makes a server request to update this file (app.vue/pages/index.vue) and remove the placeholder comment.