Add project files.

Framework/Core/Validations/IPropertyBinderCollection.cs

@@ -0,0 +1,12 @@
+using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
+
+namespace TheXamlGuy.Framework.Core
+{
+    public interface IPropertyBinderCollection : IReadOnlyCollection<PropertyBinder>
+    {
+        void Add(string key, PropertyBinder binder);
+
+        bool TryGet(string key, [MaybeNull] out PropertyBinder? value);
+    }
+}