GraphicsTester: add ScaleCanvas scenario

Add a new abstract scenario to demonstrate Canvas.Scale() with distinct X and Y scales. This test currently demonstrates a bug described by #302 where only the X scale is respected when drawing paths.

samples/GraphicsTester.Portable/Scenarios/ScaleCanvas.cs

@@ -0,0 +1,37 @@
+using Microsoft.Maui.Graphics;
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace GraphicsTester.Scenarios
+{
+	internal class ScaleCanvas : AbstractScenario
+	{
+		public ScaleCanvas() : base(720, 1024)
+		{
+		}
+
+		public override void Draw(ICanvas canvas)
+		{
+			DrawTestShapesOnScaledCanvas(canvas, 1, 1, Colors.Black);
+			DrawTestShapesOnScaledCanvas(canvas, 2, 2, Colors.Magenta);
+			DrawTestShapesOnScaledCanvas(canvas, 2, 1, Colors.Green);
+			DrawTestShapesOnScaledCanvas(canvas, 1, 2, Colors.Orange);
+		}
+
+		private void DrawTestShapesOnScaledCanvas(ICanvas canvas, float xScale, float yScale, Color color)
+		{
+			PathF path = new(100, 100);
+			path.AddArc(100, 100, 200, 200, 0, 180, true);
+			path.LineTo(150, 100);
+			path.Close();
+
+			canvas.SaveState();
+			canvas.Scale(xScale, yScale);
+			canvas.StrokeColor = color;
+			canvas.StrokeSize = 2;
+			canvas.DrawPath(path);
+			canvas.RestoreState();
+		}
+	}
+}

samples/GraphicsTester.Portable/Scenarios/ScenarioList.cs

@@ -61,6 +61,7 @@ namespace GraphicsTester.Scenarios
 						new ClipRect(),
 						new SubtractFromClip(),
 						new DimensionTest(),
+						new ScaleCanvas(),
 					};
 				}