doc: add jbergstroem as collaborator

PR-URL: #1175
Reviewed-By: Chris Dickinson <christopher.s.dickinson@gmail.com>

Author: jbergstroem

README.md

@@ -283,6 +283,7 @@ information about the governance of the io.js project, see
 * **Christian Vaagland Tellnes** ([@tellnes](https://github.com/tellnes)) <christian@tellnes.com>
 * **Robert Kowalski** ([@robertkowalski](https://github.com/robertkowalski)) <rok@kowalski.gd>
 * **Julian Duque** ([@julianduque](https://github.com/julianduque)) <julianduquej@gmail.com>
+* **Johan Bergström** ([@jbergstroem](https://github.com/jbergstroem)) <bugs@bergstroem.nu>
 
 Collaborators follow the [COLLABORATOR_GUIDE.md](./COLLABORATOR_GUIDE.md) in
 maintaining the io.js project.