Add support for RefreshIndicator

[mbartn]

This change makes the use of RefreshIndicator with LazyLoadScrollView possible.

E.g.

LazyLoadScrollView(
      onEndOfPage: () {
        //...
      },
      child: RefreshIndicator(
        onRefresh: () async {
          print('On refresh');
          return;
        },
        child: ListView.builder(
            //...
            ),
      ),
    );

[QuirijnGB]

Heya! Thanks for that! Ill have a look into it tonight and get it merge in asap!