add autodetection

Azaion.Annotator/Extensions/PointExtensions.cs

@@ -0,0 +1,9 @@
+using System.Windows;
+
+namespace Azaion.Annotator.Extensions;
+
+public static class PointExtensions
+{
+    public static double SqrDistance(this Point p1, Point p2) =>
+        (p2.X - p1.X) * (p2.X - p1.X) + (p2.Y - p1.Y) * (p2.Y - p1.Y);
+}