Adds IGNORE_DENSITY flag to windoors and railings to allow crafting on their tile (#86651)

## About The Pull Request

I am bored enough to the point where I'm diving into downstream github
issues.
Thindows have IGNORE_DENSITY but windoors and railings do not,
preventing crafting on their tiles. This ***should not*** cause any side
effects as I went through all the recipes and they still have
BLOCKS_CONSTRUCTION_DIR which should block duplicates or windows from
being constructed on the same tile, but ideally this needs another pair
of eyes.

## Why It's Good For The Game
Windoors/railings should not be preventing you from crafting sprears and
boxes on their tiles. Also parity with thindows.

## Changelog
🆑
fix: You can now craft things on tiles with windoors and railings on
them.
/🆑

code/game/objects/structures/railings.dm

@@ -4,7 +4,7 @@
 	icon = 'icons/obj/railings.dmi'
 	icon_state = "railing"
 	flags_1 = ON_BORDER_1
-	obj_flags = CAN_BE_HIT | BLOCKS_CONSTRUCTION_DIR
+	obj_flags = CAN_BE_HIT | BLOCKS_CONSTRUCTION_DIR | IGNORE_DENSITY
 	density = TRUE
 	anchored = TRUE
 	pass_flags_self = LETPASSTHROW|PASSSTRUCTURE