Add non-generic CreateNotification method

Sharp7.Rx/Utils/SignatureConverter.cs

@@ -0,0 +1,21 @@
+using System.Reactive.Linq;
+using System.Reflection;
+
+namespace Sharp7.Rx.Utils;
+
+internal static class SignatureConverter
+{
+    private static readonly MethodInfo convertToObjectObservableMethod =
+        typeof(SignatureConverter)
+            .GetMethods(BindingFlags.Public | BindingFlags.Static)
+            .Single(m => m.Name == nameof(ConvertToObjectObservable) && m.GetGenericArguments().Length == 1);
+
+    public static IObservable<object> ConvertToObjectObservable<T>(IObservable<T> obs) => obs.Select(o => (object) o);
+
+    public static IObservable<object> ConvertToObjectObservable(object observable, Type sourceType)
+    {
+        var convertGeneric = convertToObjectObservableMethod.MakeGenericMethod(sourceType);
+
+        return convertGeneric.Invoke(null, [observable]) as IObservable<object>;
+    }
+}