fix: actually expose platform.caches in adapter-cloudflare-workers

[dominikg]

#5081 already did it for adapter-cloudflare and both the docs and types for adapter-cloudflare-workers mention it, alas it wasn't returned.

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@sveltejs/adapter-cloudflare-workers	Patch

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[dominikg]

docs for cf workers runtime cache confirming that it is a global https://developers.cloudflare.com/workers/runtime-apis/cache/