Inverted horizontalChange when RTL Flow

The ManipulationDelta over X is not inverted when in RightToLeft FlowDirection. This was an unhandled bug? in UWP.

Author: Avid29

Microsoft.Toolkit.Uwp.UI.Controls/GridSplitter/GridSplitter.Events.cs

@@ -148,6 +148,11 @@ protected override void OnManipulationDelta(ManipulationDeltaRoutedEventArgs e)
             var horizontalChange = e.Delta.Translation.X;
             var verticalChange = e.Delta.Translation.Y;
 
+            if (this.FlowDirection == FlowDirection.RightToLeft)
+            {
+                horizontalChange *= -1;
+            }
+
             if (_resizeDirection == GridResizeDirection.Columns)
             {
                 if (HorizontalMove(horizontalChange))