implement escape menu

src/ui/GameWorldView.h

@@ -46,6 +46,10 @@ signals:
     void stateUpdated(Tick tick, int blocks, double speed);
     void gameOver();
     void builderModeExited();
+    void escapeMenuRequested();
+
+public:
+    double gameSpeed() const;
 
 public slots:
     void enterBuilderMode(BuildingType type);