!197 feat: 后台安装结束后退出任务栏驻留

* fix: 没有下载的时候直接退出客户端
* feat: 后台安装结束后退出任务栏驻留
* feat: 更新的时候关闭旧实例

src/widgets/downloadlistwidget.h

@@ -22,12 +22,15 @@ public:
     DownloadItem *addItem(QString name, QString fileName, QString pkgName, const QPixmap icon, QString downloadurl);
     int nowDownload = 0;
     int allDownload = 0;
+    int toDownload = 0;
     QList<DownloadItem *> getDIList();
     QList<QUrl> getUrlList();
     void m_move(int x, int y);
     explicit DownloadListWidget(QWidget *parent = nullptr);
     ~DownloadListWidget() override;
 
+    bool isDownloadInProcess();
+
 protected:
     void mouseMoveEvent(QMouseEvent *event) override;