nextPage method
Implementation
Future<SearchPage?> nextPage(YoutubeHttpClient httpClient) async {
if (initialData.continuationToken?.isEmpty == null ||
initialData.estimatedResults == 0) {
return null;
}
final data = await httpClient.sendContinuation(
'search', initialData.continuationToken!);
return SearchPage.id(queryString, _InitialData(data));
}