GREEN: implement conjured items degrading twice as fast

lib/gilded_rose.dart

@@ -93,6 +93,21 @@ class SulfurasUpdater implements ItemUpdater {
   }
 }
 
+class ConjuredItemUpdater implements ItemUpdater {
+  @override
+  void update(Item item) {
+    // Conjured items degrade twice as fast as normal items
+    _degradeQuality(item, 2);
+
+    item.sellIn -= 1;
+
+    // After sell-by date, quality degrades twice as fast (4x total)
+    if (item.sellIn < 0) {
+      _degradeQuality(item, 2);
+    }
+  }
+}
+
 class GildedRose {
   List<Item> items;
 
@@ -112,6 +127,8 @@ class GildedRose {
       return AgedBrieUpdater();
     } else if (item.name == 'Backstage passes to a TAFKAL80ETC concert') {
       return BackstagePassUpdater();
+    } else if (item.name.startsWith('Conjured')) {
+      return ConjuredItemUpdater();
     } else {
       return NormalItemUpdater();
     }