AddXxx() consistency with SignalR-SqlServer

[Yann Crumeyrolle]

With SignalR-SqlServer, the AddSqlServer() method is an extension method for the SignalRServicesBuilder class.

With SignalR-ServiceBus, the AddServiceBus() method is an extension method of the IServiceCollection.
It would be better to have the same way to add either SQL Server or the ServiceBus.

In addition, AddServiceBus() is not enough meaningful for the IServiceCollection interface.

services.AddServiceBus();

means that I add a service bus to the services, and not that I add the ServiceBus scaleout implementation for the SignalR
server.

Same issue with SignalR-Redis.