MADISON, Wis. — For Mark Johnson, the guy many believe to be the best of a group of 20 kids who shocked the hockey world 35 years ago today in Lake Placid, heaven comes on a sheet of ice measuring 32’ x 58’ just a few yards off his back patio. It’s his own man-made rink, the one he started building 12 years ago when he moved to this edge of Madison, the home of the University of Wisconsin.