Add support for streams

[tirkarthi]

Redis 5.0 will ship with streams. It's in beta now and will be stable in few months. It might be a good addition to the library and I hope it will work well with async libraries in Rust. I couldn't see any related issues or PR. Feel free to close this if it's a duplicate.

Streams reference : https://redis.io/topics/streams-intro

Thanks much for the library!

[badboy]

I played around with prototyping a stream API when streams were developed initially (I never published or even finished that though).
I'm convinced we can provide a really good API to make this all work, however I personally don't have a use case for streams on Redis currently, so I won't spend time on developing such an API.
I'd be happy to guide external contributors in implementing that though.

[lambdasqd]

I would be interested in giving this a try later this week.