chore: import upstream snapshot with attribution

tests/fixtures/sample.xaml.cs

@@ -0,0 +1,19 @@
+using System.Windows;
+
+namespace GraphifyDemo
+{
+    public partial class MainWindow : Window
+    {
+        private void Window_Loaded(object sender, RoutedEventArgs e)
+        {
+        }
+
+        private void UserNameChanged(object sender, RoutedEventArgs e)
+        {
+        }
+
+        private void Save_Click(object sender, RoutedEventArgs e)
+        {
+        }
+    }
+}