Update SWR usage example to SWR v1

[pke]

Could you please update the swr example adjusted to the new 1.x API where it no longer exports cache?

Thanks!

[sergiodxa]

I don't use SWR, or this lib, anymore, but feel free to send a PR updating the docs on how SWR works and I'll be happy to merge it

[isBatak]

@pke SWR v2 beta is out and now they have built in solution called useSWRMutation