docs: added most common status codes to redirect() doc

[GauBen]

Hey! Small QOL improvement, I often google HTTP status codes to know which one I should use. I picked the three values that should cover 99% of use cases; 302 Found is not in there because its behavior is disambiguated by 303 and 307.

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[Rich-Harris]

preview: https://svelte-dev-git-preview-kit-13301-svelte.vercel.app/

this is an automated message

[benmccann]

I'm not entirely confident that 307 doesn't have some SEO implications. I'd simplify it to remove that

[GauBen]

Search engines receiving this response will not attribute links to the original URL to the new resource, meaning no SEO value is transferred to the new URL.

Per MDN, although this is not a guarantee of any kind on Google's end

[benmccann]

I think the whole text could be squashed down to something like "Prefer 307 for temporary redirects and 308 for permanent redirects."

[GauBen]

Thanks for the review! I believe 303 is the best choice for post-action redirect, and that's what we can see in the docs too!

[GauBen]

consistency for http verbs