Removing UWP project.

Wino.Mail.WinUI/Extensions/EnumerableExtensions.cs

@@ -0,0 +1,18 @@
+using System.Collections;
+
+namespace Wino.Extensions
+{
+    public static class EnumerableExtensions
+    {
+        public static IEnumerable OfType<T1, T2>(this IEnumerable source)
+        {
+            foreach (object item in source)
+            {
+                if (item is T1 || item is T2)
+                {
+                    yield return item;
+                }
+            }
+        }
+    }
+}