doc: add iarna to collaborators

PR-URL: #4144
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
Reviewed-By: Minwoo Jung <jmwsoft@gmail.com>
Reviewed-By: Kat Marchán <kzm@sykosomatic.org>
Reviewed-By: James M Snell <jasnell@gmail.com>

Author: iarna

README.md

@@ -389,6 +389,7 @@ information about the governance of the Node.js project, see
 * [domenic](https://github.com/domenic) - **Domenic Denicola** <d@domenic.me>
 * [evanlucas](https://github.com/evanlucas) - **Evan Lucas** <evanlucas@me.com>
 * [geek](https://github.com/geek) - **Wyatt Preul** <wpreul@gmail.com>
+* [iarna](https://github.com/iarna) - **Rebecca Turner** <me@re-becca.org>
 * [isaacs](https://github.com/isaacs) - **Isaac Z. Schlueter** <i@izs.me>
 * [jbergstroem](https://github.com/jbergstroem) - **Johan Bergström** <bugs@bergstroem.nu>
 * [joaocgreis](https://github.com/joaocgreis) - **João Reis** <reis@janeasystems.com>