close method
Implementation
@override
Future<void> close() async {
saveProgress();
UDocPictureCache.instance.evictDocument(documentId);
_thumbnails.clear();
_texts.clear();
_pages.clear();
await _index?.close();
await _document?.close();
_document = null;
_renderer = null;
emit(value.copyWith(state: UDocState.closed));
}