Add docu to ts_bspline_interpolate_catmull_rom.
Add docu to ts_bspline_interpolate_catmull_rom.

msteinbeck/tinyspline,msteinbeck/tinyspline,msteinbeck/tinyspline,msteinbeck/tinyspline,msteinbeck/tinyspline,retuxx/tinyspline,msteinbeck/tinyspline,retuxx/tinyspline,msteinbeck/tinyspline,retuxx/tinyspline,msteinbeck/tinyspline