[fix] preserve user defined config and files on svelte-kit package

[ignatiusmb]

This PR fixes multiple stuff regarding package cli command

• Retain original README.md filename casing from project root.
• Preserve initial package.json and only adds exports map when it's not defined by the user.
• Force forward slash paths for exports map values

Fixes #1734
Fixes #1856

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Latest commit: 8f5294f

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

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@sveltejs/kit	Patch

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[benmccann]

this generally seems like a good idea to me, but I might leave this open for a little while to see if Rich had any other concerns in mind that I'm not aware of when he wrote it

[ignatiusmb]

Aha, I found an exception to scripts in package.json keys that we may want to exclude from the final output. It may run some of the lifecycle scripts if defined and most likely ruin the build or publish process. Other than scripts, I think everything else should be safe and have no special stuff.

---

Sure, I'm also curious for the reasons behind those specific keys. While we're here, I think the only odd one from the changes listed in the description was the "adds exports map when it's not defined by the user", so I'll explain my reasoning in case anyone's curious.

Published npm packages can now "lock" their imports (or exports in this case) to just a certain paths or modules, so there may be a package/internal used only for the modules inside and cannot be directly accessed by the end-user. There's also a reason for authors to manually specify the exports, be it only exposing some of them or adding { "browser": ... } and such. svelte-kit package forcefully overwrites this and authors would need to manually update the generated package.json again. I think the easiest thing to do without adding another config option is to just check the existence and use the built-in exports map when there's none defined.

[dummdidumm]

In #1646 I added logic for adding types to the package.json . If this was merged, should I revert the part about "define in your svelte-config.js what the types value is? I guess it would make sense to remove it.

[ignatiusmb]

I think it's a good addition for the same reason some authors might not manually specify them. Perhaps only add types and use the defined config when none is defined in the original package.json too, just like exports here?

[dummdidumm]

Looks good to me. Could you add a test verifying the new behavior? I recently did set up the infrastructure to test this area.

[ignatiusmb]

Added and adjusted the tests to also handle nested files.

I haven't added the test for the README copying, I think I prefer #1747 more. But, in case this is merged before the other, it'll still solve the initial problem in #1734, so I won't revert the changes for now

Edit: I've added test for file preservation as well, which was one of the main point of this PR.

[dummdidumm]

Let's first try to get #1747 in and then adjust this one.

[ignatiusmb]

Thanks @dummdidumm 😄, finally got it working now

[benmccann]

I merged #1747, so you can rebase this one now