Add function returning GameWorldView zoom factor

Author: falbrechtskirchinger

libs/s25main/world/GameWorldView.h

@@ -78,6 +78,7 @@ class GameWorldView
     Extent GetSize() const { return size_; }
 
     void SetZoomFactor(float zoomFactor, bool smoothTransition = true);
+    float GetZoomFactor() const { return zoomFactor_; }
     float GetCurrentTargetZoomFactor() const;
     void SetNextZoomFactor();