doc: add jkrems to collaborators

PR-URL: nodejs/node#12427
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>

Author: Jan Krems

README.md

@@ -281,6 +281,8 @@ more information about the governance of the Node.js project, see
 **Johan Bergström** <bugs@bergstroem.nu>
 * [jhamhader](https://github.com/jhamhader) -
 **Yuval Brik** <yuval@brik.org.il>
+* [jkrems](https://github.com/jkrems) -
+**Jan Krems** <jan.krems@gmail.com> (he/him)
 * [joaocgreis](https://github.com/joaocgreis) -
 **João Reis** <reis@janeasystems.com>
 * [joshgav](https://github.com/joshgav) -