Improve Features

Support save current theme setting when exit;
Use QScreen::primaryScreen() instead of QDesktopWidget to get desktop size;
Ensure only one instance will be running at the same time.

src/progressload.h

@@ -13,7 +13,7 @@ public:
     explicit ProgressLoad(QWidget *parent = nullptr);
 
     void setValue(int v);
-    void setTheme(bool dark,QColor color);
+    void setTheme(bool dark, QColor color);
 
 private:
     QWidget *m_progess;