add (very) basic main menu

src/td/display/state/MainMenuState.cpp

@@ -1,18 +1,31 @@
 #include <td/display/state/MainMenuState.h>
 
-#include <td/display/state/DebugWorldState.h>
 #include <imgui.h>
+#include <td/display/menu/MainMenu.h>
+#include <td/display/state/DebugWorldState.h>
 
 namespace td {
 
-MainMenuState::MainMenuState(Display& a_Display) : DisplayState(a_Display) {}
+MainMenuState::MainMenuState(Display& a_Display) : DisplayState(a_Display) {
+	PushState<MainMenu>();
+}
+
 MainMenuState::~MainMenuState() {}
 
 void MainMenuState::Update(float a_Delta) {
 	ImGui::Begin("MainWindow");
-	if(ImGui::Button("Start debug world"))
-		m_StateMachine.ChangeState<DebugWorldState>();
+	MainMenuStateStack::Update();
 	ImGui::End();
 }
 
+void MainMenuState::RenderBackButton() {
+	if (ImGui::Button("Back"))
+		PopState();
+}
+
+void MainMenuState::OnKeyDown(SDL_Keycode a_Key) {
+	if (a_Key == SDLK_ESCAPE)
+		PopState();
+}
+
 }  // namespace td