feat: new clone registry core function (#269)

Author: zaucy

ecsact/runtime/core.h

@@ -50,6 +50,16 @@ ECSACT_CORE_API_FN(void, ecsact_destroy_registry)
 	ecsact_registry_id registry
 );
 
+/**
+ * Creates a new registry from an existing one with all its entities and
+ * components intact.
+ */
+ECSACT_CORE_API_FN(ecsact_registry_id, ecsact_clone_registry)
+( //
+	ecsact_registry_id registry,
+	const char*        registry_name
+);
+
 /**
  * Destroy all entities
  */
@@ -296,6 +306,7 @@ ECSACT_CORE_API_FN(ecsact_stream_error, ecsact_stream)
 #	define FOR_EACH_ECSACT_CORE_API_FN(fn, ...)           \
 		fn(ecsact_create_registry, __VA_ARGS__);             \
 		fn(ecsact_destroy_registry, __VA_ARGS__);            \
+		fn(ecsact_clone_registry, __VA_ARGS__);              \
 		fn(ecsact_clear_registry, __VA_ARGS__);              \
 		fn(ecsact_create_entity, __VA_ARGS__);               \
 		fn(ecsact_ensure_entity, __VA_ARGS__);               \

ecsact/runtime/core.hh

@@ -635,6 +635,13 @@ public:
 		return ecsact_create_entity(_id);
 	}
 
+	ECSACT_ALWAYS_INLINE auto clone(const char* name) const -> registry {
+		auto cloned_registry_id = ecsact_clone_registry(_id, name);
+		auto cloned_registry = registry{cloned_registry_id};
+		cloned_registry._owned = true;
+		return cloned_registry;
+	}
+
 	template<typename Component, typename... AssocFields>
 		requires(!std::is_empty_v<Component>)
 	ECSACT_ALWAYS_INLINE auto get_component( //