Add missing source file

hecl-gui/main.cpp

@@ -0,0 +1,10 @@
+#include <QGuiApplication>
+#include "MainWindow.hpp"
+
+int main(int argc, char* argv[])
+{
+    QGuiApplication a(argc, argv);
+    MainWindow w;
+    w.show();
+    return a.exec();
+}