Implement Caching feature to the Proxy API

[trkaplan]

Multiple requests will still causes rate limit errors.
I was planning to use https://vercel.com/integrations/upstash with this project -> https://github.com/trkaplan/opensea-api-proxy for the same purpose.

You can check the proxy API commit that @ssdsr made here: e5bf582
(this is a good way to hide the API key from the client. But we need more, caching. )

Related links that may help:
vercel/next.js#12134
https://upstash.com/blog/netlify-graph-upstash