tools/chatgui: Qt5 GUI chat app stub with tray, channel list, message bubbles

tools/chatgui/src/main.cpp

@@ -0,0 +1,13 @@
+#include <QApplication>
+#include "mainwindow.h"
+
+int main(int argc, char *argv[]) {
+    QApplication app(argc, argv);
+    app.setApplicationName("Chat");
+    app.setQuitOnLastWindowClosed(false);
+
+    MainWindow w;
+    w.show();
+
+    return app.exec();
+}