readme

• for learning vtk
• 22/08/25 Tutorial_Step5.py show how to add a ruler (distance scale) to vtk, which equal to a vtkDistanceWidget;
• 22/08/26 crossSectionHair.py show how to display the orthometric plane mark line, Camera close parallelProjection, resliceCursor setThickNess=(1, 2, 3) and thicknessMode=1;