feat: add HighlightCorners mode to Prop3D and document Prop3D class functionality

src/Vtk/uLibVtkInterface.h

@@ -123,6 +123,12 @@ public:
   void SetRepresentation(Representation mode);
   void SetRepresentation(const char *mode);
 
+  enum HighlightMode {
+      HighlightPlain = 0,
+      HighlightCorners = 1
+  };
+  void SetHighlightMode(HighlightMode mode);
+
   virtual void PrintSelf(std::ostream &o) const;
 
   void ShowBoundingBox(bool show);