world: Add libshumate
libshumate is the proposed successor of libchamplain. See http://ml4711.blogspot.com/2019/01/starting-on-new-map-rendering-library.html for more info.
libshumate is the proposed successor of libchamplain. See http://ml4711.blogspot.com/2019/01/starting-on-new-map-rendering-library.html for more info.