github: Add nixward to contributors

Add @nixward to the 'contributors' team as per the contribution
nomination zephyrproject-rtos/zephyr#93261.

Signed-off-by: Stephanos Ioannidis <[email protected]>

Author: stephanosio

terraform/github-zephyrproject-rtos/team/team-members/contributors.csv

@@ -190,6 +190,7 @@ NeilChen93,member
 ngboonkhai,member
 nhutnguyenkc,member
 nikolaushuber,member
+nixward,member
 nordic-piks,member
 nordic-segl,member
 osaether,member