contains method
check if this stack contains the given page (match by VoyagerPage.path and VoyagerPage.id)
Implementation
bool contains(VoyagerPage page) {
for (final item in _items) {
if (item is VoyagerStack && item.contains(page)) {
return true;
} else if (item is VoyagerPage &&
page.id == item.id &&
page.path == item.path) {
return true;
}
}
return false;
}