What problem does this feature solve?

使用 setup sugar 设置 组件 name.

What does the proposed API look like?

<script setup="componentName"></script>
<!-- or -->
<script setup name="componentName"></script>

See here

<script>
 export default {
   name: 'componentName'
 }
</script>

<script setup>
 // script setup logic
</script>