added rootNavigator: true to asset Picker to display on top of CupertinoTabBr

Author: SchnMar

lib/src/widget/asset_picker.dart

@@ -109,8 +109,10 @@ class AssetPicker extends StatelessWidget {
           themeColor: themeColor,
           pickerTheme: pickerTheme,
         );
-        final List<AssetEntity> result =
-            await Navigator.of(context).push<List<AssetEntity>>(
+        final List<AssetEntity> result = await Navigator.of(
+          context,
+          rootNavigator: true,
+        ).push<List<AssetEntity>>(
           SlidePageTransitionBuilder<List<AssetEntity>>(
             builder: picker,
             transitionCurve: routeCurve,