SFC Composition API Syntax Sugar (<script setup>)'s URL is stale

[<script setup>](https://v3.vuejs.org/guide/migration/introduction.html#notable-new-features)'s URL should be updated to [this](https://github.com/vuejs/rfcs/blob/script-setup-2/active-rfcs/0000-script-setup.md), but if there's a newer one, use that instead.