Add project files.

Framework/Core/Observables/ObservableObject.cs

@@ -0,0 +1,14 @@
+using System.ComponentModel;
+
+namespace TheXamlGuy.Framework.Core
+{
+    public class ObservableObject : INotifyPropertyChanged
+    {
+        public event PropertyChangedEventHandler? PropertyChanged;
+
+        public virtual void OnPropertyChanged(string propertyName, object? before, object? after)
+        {
+            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
+        }
+    }
+}