Add dark theme button

include/panda_qt/main_window.hpp

@@ -1,6 +1,9 @@
 #pragma once
 
 #include <QApplication>
+#include <QMenuBar>
+#include <QPalette>
+#include <QPushBUtton>
 #include <QtWidgets>
 
 #include "panda_qt/screen.hpp"
@@ -9,8 +12,13 @@ class MainWindow : public QMainWindow {
 	Q_OBJECT
 
   private:
+	QMenuBar* menuBar = nullptr;
+	QPushButton* themeButton = nullptr;
 	ScreenWidget screen;
 
+	void setDarkTheme();
+
   public:
 	MainWindow(QApplication* app, QWidget* parent = nullptr);
+	~MainWindow();
 };