add option to shuffle schedule items (#652)

* add schedule setting

* it works

* fix tests

* update readme

* rebuild all playouts

ErsatzTV.Core/Interfaces/Scheduling/IScheduleItemsEnumerator.cs

@@ -0,0 +1,12 @@
+using ErsatzTV.Core.Domain;
+using LanguageExt;
+
+namespace ErsatzTV.Core.Interfaces.Scheduling;
+
+public interface IScheduleItemsEnumerator
+{
+    CollectionEnumeratorState State { get; }
+    ProgramScheduleItem Current { get; }
+    void MoveNext();
+    ProgramScheduleItem Peek(int offset);
+}