feat: wakeup target detection (#731)

## Summary

* If going to sleep was from the Reader view, wake up to the same book.
Otherwise, wakeup to the Home view

src/activities/reader/ReaderActivity.h

@@ -34,4 +34,5 @@ class ReaderActivity final : public ActivityWithSubactivity {
         onGoBack(onGoBack),
         onGoToLibrary(onGoToLibrary) {}
   void onEnter() override;
+  bool isReaderActivity() const override { return true; }
 };