New C# concept exercise: Queue

Hello!

As a total beginner, I first met the [`Queue`](https://learn.microsoft.com/en-us/dotnet/api/system.collections.generic.queue-1?view=net-7.0) data structure in the exercise [Circular Buffer](https://exercism.org/tracks/csharp/exercises/circular-buffer) (although I didn't solve it using it, but it looked like the simplest approach): I was wondering I we could introduce it with an _ad-hoc_ concept exercise in the C# path.

(Note: this issue is just a reminder, I will open a thread on the topic and discuss about it with the C# path maintainers)