feat: add 11 more custom items to the showcase graphic

Author: mfishma

.github/showcase_config.json

@@ -25,6 +25,102 @@
       "type": "block",
       "off_texture": "block/oak_planks",
       "on_texture": "block/oak_shelf"
+    },
+    {
+      "slot": 4,
+      "type": "block",
+      "off_texture": "item/skeleton_skull",
+      "on_texture": "block/dried_ghast_hydration_0"
+    },
+    {
+      "slot": 5,
+      "type": "item",
+      "off_texture": "item/powder_snow_bucket",
+      "on_texture": "item/sulfur_cube_bucket"
+    },
+    {
+      "slot": 6,
+      "type": "block",
+      "off_texture": "block/bricks",
+      "on_texture": "block/cinnabar_bricks"
+    },
+    {
+      "slot": 7,
+      "type": "item",
+      "off_texture": "item/iron_horse_armor",
+      "on_texture": "item/copper_nautilus_armor"
+    },
+    {
+      "slot": 8,
+      "type": "item",
+      "off_texture": "item/leather_horse_armor",
+      "on_texture": "item/netherite_horse_armor"
+    },
+    {
+      "slot": 9,
+      "type": "item",
+      "off_texture": "item/dandelion",
+      "on_texture": "item/golden_dandelion"
+    },
+    {
+      "slot": 10,
+      "type": "item",
+      "off_texture": "item/pink_petals",
+      "on_texture": "item/wildflowers"
+    },
+    {
+      "slot": 11,
+      "type": "item",
+      "off_texture": "item/iron_golem_spawn_egg",
+      "on_texture": "item/copper_golem_spawn_egg"
+    },
+    {
+      "slot": 12,
+      "type": "block",
+      "off_texture": "block/oak_planks",
+      "on_texture": "block/pale_oak_shelf"
+    },
+    {
+      "slot": 13,
+      "type": "item",
+      "off_texture": "item/music_disc_pigstep",
+      "on_texture": "item/music_disc_lava_chicken"
+    },
+    {
+      "slot": 14,
+      "type": "item",
+      "off_texture": "item/music_disc_13",
+      "on_texture": "item/music_disc_bounce"
+    },
+    {
+      "slot": 15,
+      "type": "item",
+      "off_texture": "item/pointed_dripstone",
+      "on_texture": "item/sulfur_spike"
+    },
+    {
+      "slot": 16,
+      "type": "block",
+      "off_texture": "block/end_stone",
+      "on_texture": "block/potent_sulfur"
+    },
+    {
+      "slot": 17,
+      "type": "item",
+      "off_texture": "item/soul_lantern",
+      "on_texture": "item/oxidized_copper_lantern"
+    },
+    {
+      "slot": 18,
+      "type": "block",
+      "off_texture": "block/chest",
+      "on_texture": "block/exposed_copper_chest"
+    },
+    {
+      "slot": 19,
+      "type": "block",
+      "off_texture": "block/lightning_rod",
+      "on_texture": "block/oxidized_lightning_rod"
     }
   ]
 }