fix: external URLs normalized to absolute path

[daniil4udo]

Description

This PR addresses the issue of incorrectly handling external URLs within the index.html file. When external URLs are included using the <script> tag, they get merged with the base path, resulting in malformations like /https:// (or prepended with whatever the BASE_URL is).

The changes introduced in this PR ensure that the strings are checked to determine if they are valid URLs before merging, preventing such issues.

Additional context

The problem arose when external script URLs were getting prefixed with the base path, which should not happen. This fix aims to streamline the handling of URLs and prevent potential errors caused by this incorrect merging.

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What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

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• Read the Contributing Guidelines.
• Read the Pull Request Guidelines and follow the PR Title Convention.
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[patak-dev]

In other places, we're checking against excluded cases with a new URL try catch. I think it is better to avoid it here too. See for example:

vite/packages/vite/src/node/plugins/html.ts

Line 138 in 45e4595

const isExcludedUrl = (url: string) =>

I think we'll need to check against isExternalUrl, isDataUrl, and if it starts with #.

Would you add a test case for this PR?

[daniil4udo]

As you can see somehow it still resolves to absolute path..

[patak-dev]

I think the fix is correct, just that it is better to align with the way we check for external URLs in other parts of the codebase.