addtheme：flatgray.

Gui/main.cpp

@@ -29,6 +29,11 @@ int main(int argc, char* argv[])
 
     frelayGUI w;
 
+    QFile file(":/qss/flatgray.css");
+    if (file.open(QFile::ReadOnly)) {
+        a.setStyleSheet(file.readAll());
+    }
+
     QObject::connect(&a, &SingleApplication::instanceStarted, &w, [&w]() {
         w.showNormal();
         w.raise();