scripts: checkpatch: add Co-authored-by tag
scripts: checkpatch: add Co-authored-by tag

Add Co-authored-by tag which is mainly used by Github.

Signed-off-by: Bartosz Bilas <c9544010575ed4e48ae813e3d4bf273cb2e959c4@hotmail.com>

zephyrproject-rtos/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,finikorg/zephyr,finikorg/zephyr,finikorg/zephyr,galak/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,galak/zephyr