docs: add @bjohansebas to the Security Triage team (#105)

Author: UlisesGascon

README.md

@@ -39,6 +39,7 @@ The Security Working Group is composed of two groups of members: the Security Tr
 - [Jon Church](https://github.com/jonchurch)
 - [Marco Ippolito](https://github.com/marco-ippolito)
 - [Rafael Gonzaga](https://github.com/RafaelGSS)
+- [Sebastian Beltran](https://github.com/bjohansebas)
 - [Ulises Gascón](https://github.com/UlisesGascon)
 - [Wes Todd](https://github.com/wesleytodd)