feat: display errors in SWRCache

[koba04]

fixes #5 This PR is to display errors in SWR cache.

TODO:

• [x] display error
• [x] store error in the cache store of SWRDevTools

error is a string

error is an object

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[koba04]

You can try this on https://swr-devtools-git-feat-display-error-koba04.vercel.app?error=true