MNT: Update mailmap

Author: effigies

.mailmap

@@ -67,6 +67,7 @@ Gio Piantoni <github@gpiantoni.com>
 Guillaume Flandin <guillaume.flandin@gmail.com>
 Hans Johnson <hans-johnson@uiowa.edu> <hans.j.johnson@gmail.com>
 Horea Christian <horea.christ@yandex.com> <h.chr@mail.ru>
+Hrvoje Stojic <hrvoje.stojic@protonmail.com>
 Isaac Schwabacher <ischwabacher@wisc.edu>
 Jakub Kaczmarzyk <jakubk@mit.edu>
 James Kent <james-kent@uiowa.edu>