adding a shape that can display a item or a block (#1365)

added 'polygon', 'item' and 'block' to scarpet rendered shapes

src/main/java/carpet/mixins/ShulkerBoxAccessMixin.java

@@ -0,0 +1,11 @@
+package carpet.mixins;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.gen.Accessor;
+
+import net.minecraft.client.model.ShulkerModel;
+
+@Mixin(net.minecraft.client.renderer.blockentity.ShulkerBoxRenderer.class)
+public interface ShulkerBoxAccessMixin {
+    @Accessor("model")
+    ShulkerModel getModel();
+}