PubSub Interface

[cha-king]

Hi there! 👋

I'm currently using interfaces provided from this package such as UniversalClient in order to mock Redis in unit testing. This has been working quite well, however, I've hit a bit of a roadblock testing Subscribe on account of there not being a PubSub interface that the UniversalClient interface can reference?

Is this intentionally omitted or could this be included in this package?

Thanks!