Split out implementation and interfaces into a separate packages

[tugberkugurlu]

It would be great to have a separate package for Interfaces (e.g. Redbus.Abstractions). The main need I have for this is that I want my domain project to have a reference to Redbus.Abstractions package but don't want it to have a reference to concrete implementation of the event bus so that it prevents direct coupling to the implementation.

I am happy to contribute this but wanted to check with you first to see if this would be something you are up to having.

[mxjones]

@tugberkugurlu yes that sounds good to me 👍 - You can go ahead with the changes neccessary for this if you want and submit a PR and I will sort out the NuGet package related stuff, thanks!

[facundofarias]

True @tugberkugurlu! Same happening here!