How to use application will terminate in macOS

Issue #601

On Xcode 11, applicationWillTerminate is not called because of default automatic termination on in Info.plist. Removing NSSupportsSuddenTermination to trigger will terminate notification

func applicationWillTerminate(_ notification: Notification) {
    save()
}

<key>NSSupportsAutomaticTermination</key>
<true/>
<key>NSSupportsSuddenTermination</key>
<true/>