Haunted dungeon template (#23768)

* haunted dungeon

* Initial work

Still needs prefab gen work to make it interesting.

* ime a worm

* weh

* Work

* Slight tweaks

---------

Co-authored-by: metalgearsloth <comedian_vs_clown@hotmail.com>

Content.Shared/Procedural/DungeonRoom.cs

@@ -4,7 +4,7 @@ namespace Content.Shared.Procedural;
 
 public sealed record DungeonRoom(HashSet<Vector2i> Tiles, Vector2 Center, Box2i Bounds, HashSet<Vector2i> Exterior)
 {
-    public List<Vector2i> Entrances = new();
+    public readonly List<Vector2i> Entrances = new();
 
     /// <summary>
     /// Nodes adjacent to tiles, including the corners.