feat(Modal): pass transitioning prop to slots

[typed-sigterm]

🔗 Linked issue

close #4759

❓ 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)
• ✨ 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

As the title said

📝 Checklist

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

[pkg-pr-new]

npm i https://pkg.pr.new/@nuxt/ui@4760

commit: 00336b8

[J-Michalek]

We would also need to implement this to similar components such as Drawer and Slideover.

[benjamincanac]

Would you mind explaining why you need a transitioning slot prop? 🤔

[typed-sigterm]

<UModal>
  <template #body="{ transitioning }">
    <UForm v-slot="{ loading }" @submit="submit">
      <UButton :loading="loading || transitioning" type="submit">Submit</button>
    </UForm>
  </template>
</UModal>

This prevents the submit button's loading state from disappearing before the modal closes.