Feat/add draggable property cupertino sheet route (#357)

* feat: add draggable property to CupertinoSheetRoute 

it seems like a nice addition to me to let users customise this behaviour, also it might mitigate some scrolling issues users have.

* chore: reformatted changed content

---------

Co-authored-by: Jaime Blasco <jaimeblasco97@gmail.com>

@@ -101,6 +101,7 @@ class CupertinoSheetRoute<T> extends SheetRoute<T> {
     Color? backgroundColor,
     super.maintainState = true,
     super.fit,
+    super.draggable = true,
   }) : super(
           builder: (BuildContext context) {
             return _CupertinoSheetDecorationBuilder(
@@ -113,9 +114,6 @@ class CupertinoSheetRoute<T> extends SheetRoute<T> {
           initialExtent: initialStop,
         );
 
-  @override
-  bool get draggable => true;
-
   final SheetController _sheetController = SheetController();
 
   @override