Move source files to src directory

src/about.h

@@ -0,0 +1,22 @@
+#ifndef ABOUT_H
+#define ABOUT_H
+
+#include <QDialog>
+
+class About : public QDialog
+{
+    Q_OBJECT
+public:
+    About(QWidget *parent = nullptr);
+};
+
+class HelpDialog : public QDialog
+{
+    Q_OBJECT
+public:
+    HelpDialog(QWidget *parent = nullptr);
+};
+
+QString getVersion();
+
+#endif // ABOUT_H