Release v0.6.9: notify about updates and fix Settings scroll flicker

src/app.h

@@ -95,6 +95,7 @@ class App
     std::thread updateWorker;
     bool updateRunning{}, installingUpdate{};
     std::wstring availableUpdate, notifiedUpdate;
+    bool (*updateNotifier)(const std::wstring &){};
     bool stop{};
     UINT taskbarCreated{};
     uint64_t pendingAutoVersion{};