Allow creating unhidden traps in special levels

des.trap({ type = "rust", seen = true });

doc/lua.adoc

@@ -741,10 +741,13 @@ Example:
 
 === trap
 
+Create a trap.
+
 Example:
 
  des.trap({ type = "hole", x = 1, y = 1 });
  des.trap({ type = "hole", coord = {2, 2} });
+ des.trap({ type = "web", coord = {2, 2}, spider_on_web = false, seen = true });
  des.trap("hole", 3, 4);
  des.trap("level teleport", {5, 8});
  des.trap("rust")