Add Gelson to the AUTHORS.md file (#447)

Author: Souza-junior

AUTHORS.md

@@ -8,4 +8,5 @@ order by last name) and are considered "The Verde Developers":
 * [Lindsey Heagy](https://github.com/lheagy) - University of California Berkeley, Department of Statistics, USA (ORCID: [0000-0002-1551-5926](https://www.orcid.org/0000-0002-1551-5926))
 * [Jesse Pisel](https://github.com/jessepisel) - University of Texas at Austin, College of Natural Sciences, USA (ORCID: [0000-0002-7358-0590](https://www.orcid.org/0000-0002-7358-0590))
 * [Santiago Soler](https://github.com/santisoler) - CONICET, Argentina; Instituto Geofísico Sismológico Volponi, Universidad Nacional de San Juan, Argentina (ORCID: [0000-0001-9202-5317](https://www.orcid.org/0000-0001-9202-5317))
+* [Gelson Ferreira Souza-Junior](https://github.com/Souza-junior) - Universidade de São Paulo, Brazil (ORCID: [0000-0002-5695-4239](https://orcid.org/0000-0002-5695-4239))
 * [Leonardo Uieda](https://github.com/leouieda) - Universidade de São Paulo, Brazil (ORCID: [0000-0001-6123-9515](https://www.orcid.org/0000-0001-6123-9515))