Update Azure SignalR hosting readme to note ConnectionString usage and client methods to use

[timheuer]

The SignalR resource sets the connection string information as a ConnectionStrings__{name} But the Microsoft.Azure.SignalR client by default looks for Azure:SignalR:ConnectionString -- there is an override to supply it and the developer would have to know now to use

.AddAzureSignalR(builder.Configuration.GetConnectionString("signalr"));

Should we emit the default expected config setting instead? If not, convert this to an issue to update readme/docs on this resource to note the client consumption side

[christiannagel]

Instead of using .AddAzureSignalR(), I was using .AddNamedAzureSignalR("signalr") which is documented to read form connectionstrings.

This is also documented here: https://learn.microsoft.com/en-us/dotnet/aspire/real-time/azure-signalr-scenario?tabs=dotnet-cli#express-the-resource

[timheuer]

Perfect. Converting this to updating the readme to point this out