add 'model-name' item property

src/items/ItemDef.cpp

@@ -14,4 +14,5 @@ void ItemDef::cloneTo(ItemDef& dst) {
     dst.icon = icon;
     dst.placingBlock = placingBlock;
     dst.scriptName = scriptName;
+    dst.modelName = modelName;
 }

src/items/ItemDef.hpp

@@ -35,6 +35,8 @@ struct ItemDef {
     std::string placingBlock = "core:air";
     std::string scriptName = name.substr(name.find(':') + 1);
 
+    std::string modelName = name + ".model";
+
     struct {
         itemid_t id;
         blockid_t placingBlock;