Update AUTHORS.md

Author: simongravelle

AUTHORS.md

@@ -1,12 +1,7 @@
 ## Authors
 
-### Project creator
-
-- [Simon Gravelle](https://github.com/simongravelle),
+- [Simon Gravelle](https://github.com/simongravelle) (corresponding author),
   Univ. Grenoble Alpes, CNRS, LIPhy, 38000 Grenoble, France
-
-### Contributors
-
 - [Jacob R. Gissinger](https://www.stevens.edu/profile/jgissing),
   Stevens Institute of Technology, Hoboken, NJ 07030, USA
 - [Axel Kohlmeyer](https://sites.google.com/site/akohlmey),