add entity events: on_spawn, on_despawn

src/objects/EntityDef.hpp

@@ -6,6 +6,12 @@
 
 #include "../typedefs.hpp"
 
+struct entity_funcs_set {
+    bool init : 1;
+    bool on_spawn : 1;
+    bool on_despawn : 1;
+};
+
 struct EntityDef {
     /// @brief Entity string id (with prefix included)
     std::string const name;
@@ -15,6 +21,7 @@ struct EntityDef {
     
     struct {
         entityid_t id;
+        entity_funcs_set funcsset;
     } rt;
     
     EntityDef(const std::string& name) : name(name) {}