Provide reactive streams category

[wtrocki]

Reactive streams (mutiny in quarkus) provides very good abstraction for even streaming.
We can consider introducing that as separate category:

https://github.com/reactive-streams/reactive-streams-js

For java:
https://smallrye.io/smallrye-mutiny/index.html

Apart from reactive streams spec we have cloud events spec (this is somehow different but still falls into category of event platform wrappers).

https://github.com/cloudevents/spec

[mhdawson]

I know we have support for Node.js in cloudevents as @lholmquist is involved in that project.

Good idea to have a section on streams/reactive.