Fixed initial colour of filter button

inabox.wpf/DynamicGrid/ColumnFilter/DynamicGridColumnFilterUIButton.cs

@@ -25,7 +25,7 @@ public class DynamicGridColumnFilterUIButton : Button
     {
         Filter = filter;
 
-        Content = new Image { Source = _filterImage };
+        Content = new Image { Source = filter.IsFiltered() ? _filterSetImage : _filterImage };
         Background = Colors.Transparent.ToBrush();
         BorderThickness = new(0);
         MaxHeight = 23;