feat: introduce exportRender feature

[zhiyuanzmj]

<script setup lang="tsx">
export default () => <div>ok</div>
</script> 

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[changeset-bot]

🦋 Changeset detected

Latest commit: ad90198

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 5 packages

Name	Type
@vue-macros/export-render	Minor
@vue-macros/volar	Minor
unplugin-vue-macros	Patch
@vue-macros/nuxt	Patch
@vue-macros/astro	Patch

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[sxzz]

Thanks for the contribution! However, it would be better to have a discussion before sending a PR with new features.

BTW, you can push new branches into this repo without forking.