Thin railings (#3823)

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## About The Pull Request
Adds thinner railings as a mapping option

![image](https://github.com/user-attachments/assets/e798027e-6efe-4374-b5b3-b81df9d73ca8)

Adds wooden railings sprites that aren't a recolored normal railing

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## Why It's Good For The Game
mapping tools for aesthetic


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## Changelog

:cl: Spooky, Erika
add: thin railings
imageadd: spooky: thin railing sprites and sprites for wooden railings
/:cl:

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code/game/objects/structures/railings.dm

@@ -142,12 +142,12 @@
 
 /obj/structure/railing/wood
 	name = "wooden railing"
-	color = "#A47449"
+	icon_state = "wood_railing_thin"
 	buildstack = /obj/item/stack/sheet/mineral/wood
 
 /obj/structure/railing/corner/wood
 	name = "wooden railing"
-	color = "#A47449"
+	icon_state = "wood_corners_thin"
 	buildstack = /obj/item/stack/sheet/mineral/wood
 
 /obj/structure/railing/modern
@@ -202,3 +202,9 @@
 
 /obj/structure/railing/thick/corner
 	icon_state = "railing_thick_corner"
+
+/obj/structure/railing/thin
+	icon_state = "railing_thin"
+
+/obj/structure/railing/thin/corner
+	icon_state = "railing_thin_corner"