fix(scan): do not match 'export default' in comments

[ygj6]

fix #4598

Description

If the script code happens to contain export default in comments, then export default {} will not be added at the end of line.
Just like the issue #4598 :

<script setup>
import { provide } from 'vue'

// const count = ref(1)
// const plusOne = computed(() => count.value + 1)
// export default {
//     computed: {
//         notification_width: function () {
//             return Math.min(600, Math.max(document.documentElement.clientWidth, window.innerWidth || 0)) || 'px' //fit on mobile
//         }
//     },

</script>

vite/packages/vite/src/node/optimizer/scan.ts

Lines 241 to 243 in eb2e41b

	if (!js.includes(`export default`)) {
	js += `\nexport default {}`
	}

My current solution refers to PR: #4088 . Empty the singleline & multiline comments first, using the code without comments to match.

Additional context

I have considered adding test cases, but meanwhile I noticed that current unit tests are only for regular expressions, so I don't add them at the moment.

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What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

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