Add support for item tab icon suppliers.

Author: Darkhax

Common/src/main/java/net/darkhax/bookshelf/api/item/ICreativeTabBuilder.java

@@ -22,6 +22,11 @@ default BT setIcon(ItemStack icon) {
         return setIcon(() -> icon);
     }
 
+    default BT setIconItem(Supplier<ItemLike> iconSupplier) {
+
+        return this.setIcon(() -> new ItemStack(iconSupplier.get()));
+    }
+
     BT setIcon(Supplier<ItemStack> iconSupplier);
 
     BT setEnchantmentCategories(EnchantmentCategory... categories);