toggleBookmark method
Toggle bookmark for a page. Returns true if added, false if removed.
Implementation
Future<bool> toggleBookmark(int page) async {
final raw = await storage.getStringList(_bookmarkKey);
final pages = raw.toSet();
final key = page.toString();
final added = !pages.contains(key);
if (added) {
pages.add(key);
} else {
pages.remove(key);
}
await storage.setStringList(_bookmarkKey, pages.toList());
return added;
}