gives the voidwalker nightvision (#96264)

## About The Pull Request
Gives the voidwalker darkvision

## Why It's Good For The Game
Why wasn't this a thing before?? 
It should have been a thing before.
Oh well, minor oversight.

## Changelog
🆑
qol: gives the voidwalker nightvision. Why wasn't this a thing before??
/🆑

code/modules/antagonists/voidwalker/voidwalker_mob.dm

@@ -40,6 +40,11 @@
 	hud_possible = list(ANTAG_HUD)
 	sight = SEE_TURFS | SEE_MOBS
 
+	//purplish tint night vision because the voidwalker is purple
+	lighting_cutoff_red = 30
+	lighting_cutoff_green = 15
+	lighting_cutoff_blue = 30
+
 	/// Color of our regen outline
 	var/regenerate_colour = COLOR_GRAY