Add custom head models

src/main/java/moe/nea/firmament/mixins/custommodels/BakedModelDataHolderBuiltin.java

@@ -0,0 +1,33 @@
+/*
+ * SPDX-FileCopyrightText: 2024 Linnea Gräf <nea@nea.moe>
+ *
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+package moe.nea.firmament.mixins.custommodels;
+
+import moe.nea.firmament.features.texturepack.BakedModelExtra;
+import net.minecraft.client.render.model.BakedModel;
+import net.minecraft.client.render.model.BuiltinBakedModel;
+import org.jetbrains.annotations.Nullable;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Unique;
+
+@Mixin(BuiltinBakedModel.class)
+public class BakedModelDataHolderBuiltin implements BakedModelExtra {
+
+    @Unique
+    private BakedModel headModel;
+
+
+    @Nullable
+    @Override
+    public BakedModel getHeadModel_firmament() {
+        return headModel;
+    }
+
+    @Override
+    public void setHeadModel_firmament(@Nullable BakedModel headModel) {
+        this.headModel = headModel;
+    }
+}