Build fix

Author: rds1983

src/Myra/Utility/UIUtils.cs

@@ -1,8 +1,15 @@
-using Microsoft.Xna.Framework;
-using Myra.Graphics2D.UI;
+using Myra.Graphics2D.UI;
 using System;
 using System.Collections.Generic;
 
+#if MONOGAME || FNA
+using Microsoft.Xna.Framework;
+#elif STRIDE
+using Stride.Core.Mathematics;
+#else
+using System.Drawing;
+#endif
+
 namespace Myra.Utility
 {
 	internal static class UIUtils