Display download/upload speed in dock icon

Implementation is based on Transmission sources.

Closes #2761
Closes #3671
Closes #7098
Closes #11350
Closes #18527

PR #19595

src/gui/mainwindow.h

@@ -61,6 +61,13 @@ class TorrentCreatorDialog;
 class TransferListFiltersWidget;
 class TransferListWidget;
 
+#ifdef Q_OS_MACOS
+namespace MacUtils
+{
+    class Badger;
+}
+#endif
+
 namespace Net
 {
     struct DownloadResult;
@@ -245,4 +252,7 @@ private:
 
     QTimer *m_programUpdateTimer = nullptr;
 #endif
+#ifdef Q_OS_MACOS
+    std::unique_ptr<MacUtils::Badger> m_badger;
+#endif
 };