Redirect old docs

[benmccann]

This returns a 404: https://svelte.dev/faq
As does this: https://svelte.dev/docs/typescript#enhancing-built-in-dom-type

We should probably improve some of the best-effort redirects. In #595 I commented some that are not good now. Perhaps we can use client-side hash redirects to improve things
And the types/modules pages are wrong: https://github.com/sveltejs/svelte.dev/pull/538/files#r1811558592 (see sveltejs/kit#12862 to manually fix them in the kit docs)

#556 made hashes case-insensitive, but there are still places where punctuation or other things changed. E.g. https://svelte.dev/docs/kit/form-actions#progressive-enhancement-use-enhance has a punctuation change

We also need to review all the learn.svelte.dev redirects (#619)

[benmccann]

The old types page gets redirected to https://svelte.dev/docs/kit/@sveltejs-kit, which is largely correct. The public-types- and private-types- prefixes could be stripped and capitalization is different.

https://kit.svelte.dev/docs/types#public-types-loadevent
https://kit.svelte.dev/docs/types#private-types-cspdirectives

The one exception is that the Config and KitConfig types now live on https://svelte.dev/docs/kit/configuration. But the old docs for those were so useless that I doubt anyone linked to them and I'm not too worried about redirecting them

[benmccann]

The old modules page is another story. It needs a placeholder redirection page. E.g.:

• https://kit.svelte.dev/docs/modules#$app-forms-deserialize now goes to https://svelte.dev/docs/kit/$app-forms#deserialize
• https://kit.svelte.dev/docs/modules#sveltejs-kit-node-createreadablestream now goes to https://svelte.dev/docs/kit/@sveltejs-kit-node#createReadableStream