feat: add taskbar flashing on new notifications (#1209)

Co-authored-by: V <vendicated@riseup.net>

src/shared/settings.d.ts

@@ -20,6 +20,7 @@ export interface Settings {
     hardwareVideoAcceleration?: boolean;
     arRPC?: boolean;
     appBadge?: boolean;
+    enableTaskbarFlashing?: boolean;
     disableMinSize?: boolean;
     clickTrayToShowHide?: boolean;
     customTitleBar?: boolean;