move Windows app to Windows folder, create folder for Web, create simplest web api service

Windows/Azaion.Annotator/Extensions/CanvasExtensions.cs

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+using System.Windows;
+using System.Windows.Controls;
+using System.Windows.Media;
+
+namespace Azaion.Annotator.Extensions;
+
+public static class CanvasExtensions
+{
+    public static readonly DependencyProperty PercentPositionProperty =
+        DependencyProperty.RegisterAttached("PercentPosition", typeof(Point), typeof(CanvasExtensions), 
+            new PropertyMetadata(new Point(0, 0), OnPercentPositionChanged));
+    
+    public static readonly DependencyProperty PercentSizeProperty =
+        DependencyProperty.RegisterAttached("PercentSize", typeof(Point), typeof(CanvasExtensions), 
+            new PropertyMetadata(new Point(0, 0), OnPercentSizeChanged));
+
+    private static void OnPercentSizeChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
+    {
+        
+    }
+    
+    public static void SetPercentPosition(DependencyObject obj, Point value) => obj.SetValue(PercentPositionProperty, value);
+    
+    private static void OnPercentPositionChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
+    {
+        if (!(d is FrameworkElement element)) return;
+        if (!(VisualTreeHelper.GetParent(element) is Canvas canvas)) return;
+
+        canvas.SizeChanged += (s, arg) =>
+        {
+            var percentPosition = (Point)element.GetValue(PercentPositionProperty);
+            var xPosition = percentPosition.X * canvas.ActualWidth - element.ActualWidth / 2;
+            var yPosition = percentPosition.Y * canvas.ActualHeight - element.ActualHeight / 2;
+            Canvas.SetLeft(element, xPosition);
+            Canvas.SetTop(element, yPosition);
+        };
+    }
+}