gui: Add new AboutDialog to show our licenses "paperwork"

gui/aboutdialog.h

@@ -0,0 +1,12 @@
+#ifndef ABOUTDIALOG_H
+#define ABOUTDIALOG_H
+#include <QDialog>
+
+class AboutDialog : public QDialog
+{
+	Q_OBJECT
+  public:
+	AboutDialog(QWidget *parent = nullptr);
+};
+
+#endif // ABOUTDIALOG_H