Add behavior(HitTestBehavior) to ReorderableListener

[mono0926]

Before this change, transparent area of ReorderableListener doesn't react to onPointerDown.

This can be reproduced by commenting out this line:

flutter_reorderable_list/example/lib/main.dart

Line 194 in 327f51e

color: Color(0x08000000),

And the problem is fixed by specifying behavior: HitTestBehavior.opaque, so that parameter is needed.

    Widget dragHandle = draggingMode == DraggingMode.iOS
        ? ReorderableListener(
            child: Container(
              padding: EdgeInsets.only(right: 18.0, left: 18.0),
//              color: Color(0x08000000),
              child: Center(
                child: Icon(Icons.reorder, color: Color(0xFF888888)),
              ),
            ),
            // Add this
            behavior: HitTestBehavior.opaque,
          )
        : Container();

Original code:

flutter_reorderable_list/example/lib/main.dart

Lines 190 to 200 in 327f51e

	Widget dragHandle = draggingMode == DraggingMode.iOS
	? ReorderableListener(
	child: Container(
	padding: EdgeInsets.only(right: 18.0, left: 18.0),
	color: Color(0x08000000),
	child: Center(
	child: Icon(Icons.reorder, color: Color(0xFF888888)),
	),
	),
	)
	: Container();