fix: copy _headers and _redirects from project root instead of /static

[eltigerchino]

closes #12216

This PR documents the fact that the two Cloudflare Pages specific files need to be excluded from the service worker's files or the service worker will fail to register if it tries to add them to the cache. This is because the files are not publicly available after the app is deployed and the service worker will error if it can't find them from the internet.

It would be nicer if we could use the adapter to exclude them but I don't know of an easy way to hook into the service worker build process or to modify the final output.

Alternatively, we could stop encouraging _headers and _redirects files in the /static directory as mentioned in the docs, and have the adapter read/copy them from the root of the project instead. Technically, they never should have been in the /static directory since they are not meant to be public files. This would be a breaking change but it does fix this issue in a better way.

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[Rich-Harris]

preview: https://svelte-dev-git-preview-kit-13227-svelte.vercel.app/

this is an automated message

[dummdidumm]

and have the adapter read/copy them from the root of the project instead

So people would no longer do

src/
etc/
static/
   _headers

they would put it in the root directly?

src/
etc/
_headers

Do you remember why we did it originally by putting it in static? I think it makes sense to not have them in static because as you say that's not where they will end up eventually.

[eltigerchino]

and have the adapter read/copy them from the root of the project instead

So people would no longer do

src/
etc/
static/
   _headers

they would put it in the root directly?

src/
etc/
_headers

Yes, that's right.

Do you remember why we did it originally by putting it in static?

I don't think it was ever intentional but it was the only way to have the files copied over to the root of the build output automatically without changes in the adapter.

[eltigerchino]

I've changed it so that we copy the files from the project root now instead of relying on /static.