Fix app focus lost on Windows when exiting monitor fullscreen

Related to #1390

src/monitor/monitor.cpp

@@ -962,6 +962,7 @@ void Monitor::slotSwitchFullScreen(bool minimizeOnly)
         m_glWidget->showNormal();
         auto *lay = static_cast<QVBoxLayout *>(layout());
         lay->insertWidget(0, m_glWidget, 10);
+        activateWindow();
         setFocus();
     }
 }