add parse to avaloniaxamlloader

src/Markup/Avalonia.Markup.Xaml/AvaloniaXamlLoader.cs

@@ -7,5 +7,10 @@
         AvaloniaXamlLoaderPortableXaml
 #endif
     {
+        public static object Parse(string xaml)
+                => new AvaloniaXamlLoader().Load(xaml);
+
+        public static T Parse<T>(string xaml)
+                     => (T)Parse(xaml);
     }
 }