Tutorial: going down and up stairs

Adds the second tutorial level, tut-2.lua

dat/dungeon.lua

@@ -317,13 +317,17 @@ dungeon = {
    },
    {
       name = "The Tutorial",
-      base = 1,
+      base = 2,
       flags = { "mazelike", "unconnected" },
       levels = {
          {
             name = "tut-1",
             base = 1,
          },
+         {
+            name = "tut-2",
+            base = 2,
+         },
       }
    },
 }