feat: Lazy incremental EPUB section indexing (#2452)

Co-authored-by: Uri Tauber <uritaube@gmail.com>
Co-authored-by: Julia Nguyen <julia@uxj.io>

src/activities/ActivityResult.h

@@ -43,6 +43,10 @@ struct PageResult {
 struct ProgressChangeResult {
   int spineIndex = 0;
   int page = 0;
+  int totalPages = 0;
+  std::string xpath;
+  float percentage = 0.0f;
+  bool hasSavedProgress = false;
 };
 
 enum class NetworkMode;