Add lettuce Redis client

[mp911de]

No description provided.

[smaldini]

@reactive-streams/contributors @viktorklang I wonder if the list could benefit from a refresh in general, or maybe a dedicate page that lists reactive-streams ready library ?

[viktorklang]

@smaldini @mp911de We can't retroactively update the 1.0.0 release notes :)
I think Stephane has a good idea, how about we add a document listing known implementations?

As for Lettuce, (I haven't had a chance to look at the implementations), is all RS implementations checked with the TCK?

[mp911de]

@viktorklang lettuce comes just with own Publisher and Subscription implementations, no processors. TCK integration is here.