fix(nuxt): get fallback for <DevOnly> from parsed html

[ineshbose]

🔗 Linked issue

#20817 (comment)

❓ 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)

📚 Description

It should now allow the documented example as well:

    <DevOnly>
      <!-- arrows before fallback or... -->
       <ClientOnly>
          <template #fallback>
            <div>test</div>
          </template>
      </ClientOnly>
      <template #fallback>
        <div></div>
      </template>
    </DevOnly>

📝 Checklist

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

[nuxt-studio]

✅ Live Preview ready!

Name	Edit	Preview	Latest Commit
Nuxt Docs	Edit on Studio ↗︎	View Live Preview	bca1590

[ineshbose]

An app.vue that should cover the bases to test:

<script setup lang="ts">
</script>

<template>
  <!-- Edit this file to play around with Nuxt but never commit changes! -->
  <div>
    Nuxt 3 Playground
    <DevOnly>standard</DevOnly>
    <DevOnly>
      standard
      <template #fallback>
        <span>Fallback content</span>
      </template>
    </DevOnly>

    <DevOnly>
      <div>Element</div>
    </DevOnly>
    <DevOnly>
      <div>Element</div>
      <!-- comment -->
      <template #fallback>Fallback content2</template>
    </DevOnly>
    <DevOnly>
      Empty fallback
      <!-- empty fallback -->
      <template #fallback></template>
    </DevOnly>

    <DevOnly>
      <div>dev only</div>
      <ClientOnly>
        client only
        <div>client div</div>
        <template #fallback>
          <div>client fallback</div>
        </template>
      </ClientOnly>
      <template #fallback>
        <div>dev fallback</div>
      </template>
    </DevOnly>
  </div>
</template>

<style scoped>
</style>

[huang-julien]

👍 working wonderfully on my side