fix: handle functional generate.routes

[danielroe]

🔗 Linked issue

resolves #472

❓ Type of change

• 📖 Documentation (updates to the documentation or readme)
• 🐞 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)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

Users who want to programmatically determine what routes should be prerendered should use a hook to do so:

import { defineNuxtConfig } from '@nuxt/bridge'

export default defineNuxtConfig({
  hooks: {
    async 'nitro:config' (config) {
      const routes = await getRoutes()
      config.prerender.routes.push(...routes)
    }
  }
})

In the mean time, for backward compatibility, we can call the generate.routes function.

📝 Checklist

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

[pi0]

We might intoroduce better nitro hook (in prerender: namespace) to allow extending async hooks. nitro:config is also for dev and nornal build.

[danielroe]

Agreed - I think it would be good to have such a hook. Updating this section to avoid calling it in dev/prepare.