Changes the default ghost lighting, makes it a preference (#65352)

* Changes the default ghost lighting, makes it a preference

I think the way ghost lighting looks right now is really crummy.
It's dark enough you can see where the shadows should be, but it's just
bright enough for everything to look like dog poo

A lot of what makes the game look nice is the depth of the lighting
and if we just hide that for observers we're shooting ourselves in the
foot.

I'm also making it a game preference, so if someone wants to have bad
opinions they can easily.

code/modules/client/preferences/ghost_lighting.dm

@@ -0,0 +1,28 @@
+GLOBAL_LIST_INIT(ghost_lighting_options, list(
+	"Fullbright" = LIGHTING_PLANE_ALPHA_INVISIBLE,
+	"Night Vision" = LIGHTING_PLANE_ALPHA_MOSTLY_INVISIBLE,
+	"Darker" = LIGHTING_PLANE_ALPHA_MOSTLY_VISIBLE,
+	"Normal" = LIGHTING_PLANE_ALPHA_VISIBLE,
+))
+
+/// How bright a ghost's lighting plane is
+/datum/preference/choiced/ghost_lighting
+	category = PREFERENCE_CATEGORY_GAME_PREFERENCES
+	savefile_key = "ghost_lighting"
+	savefile_identifier = PREFERENCE_PLAYER
+
+/datum/preference/choiced/ghost_lighting/create_default_value()
+	return "Darker"
+
+/datum/preference/choiced/ghost_lighting/init_possible_values()
+	var/list/values = list()
+	for(var/option_name in GLOB.ghost_lighting_options)
+		values += option_name
+	return values
+
+/datum/preference/choiced/ghost_lighting/apply_to_client(client/client, value)
+	var/mob/current_mob = client?.mob
+	if(!isobserver(current_mob))
+		return
+	current_mob.lighting_alpha = current_mob.default_lighting_alpha()
+	current_mob.update_sight()