[fix] replace kit.paths.base if it runs on localhost

[baseballyama]

fix: #2230

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Explain What I Did

In this PR #2189, the way of handle for kit.paths.assets in svelte.config.js was changed.
After that, the issue #2230 comes.

I think this issue is only a problem in a dev environment like localhost.
(Please check details at here)

So I just handled this issue as like workaround code.

As an alternative way, we can modify module bunder (like Vite).
In this case, we can create a folder which is the value of kit.paths.assets as the parent of the _app folder. (And maybe something more.)
But in my opinion, we will have a chance to handle this issue for each module bundler.
This is just a little bit troublesome.
Therefore I choose this simple way.

So could you please review this way is reasonable?
Or should I modify Vite or somewhere else?

MEMO

1. I don't know how to do the brawser test with npm run dev command. Please tell me how can I add a test for it.

2. When I execute pnpx changeset, it shows If you are unsure if this is correct, contact the package's maintainers before committing this changeset, so now I didn't create changeset. (After getting a review comment, I will create it.)

Thank you!

[changeset-bot]

🦋 Changeset detected

Latest commit: e56abff

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

This PR includes changesets to release 1 package

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@sveltejs/kit	Patch

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[baseballyama]

I realized that just using replace() has chance to mis-replacement if middle of file path has path which is same as base path.
So I will fix it but I'm happy if someone review for this fixing policy!

edit: I fixed it up.

[dreitzner]

Lgtm

[benmccann]

Another PR to fix this issue has been submitted to fix paths.base at #2407. I'm not that familiar with this code and haven't looked closely at either PR yet to know which makes more sense

[baseballyama]

I discussed about this PR with the author of #2407.
And I think we should adopt #2407 instead of this PR.
Therefore I will close this PR after merge #2407 if nothing happens.

[benmccann]

Ok, I'll just go ahead and close it now then