Support retrieving entity count from ecs::container

libs/ecs/include/psemek/ecs/container.hpp

@@ -381,6 +381,8 @@ namespace psemek::ecs
 		template <typename ... Components>
 		std::size_t memory_usage();
 
+		std::size_t entity_count();
+
 		std::size_t cache_count();
 
 		std::size_t table_count();

libs/ecs/include/psemek/ecs/detail/entity_list.hpp

@@ -32,6 +32,11 @@ namespace psemek::ecs::detail
 			return entities_;
 		}
 
+		std::size_t size() const
+		{
+			return entities_.size() - free_ids_.size();
+		}
+
 	private:
 		std::vector<entity_data> entities_;
 		std::vector<entity_id> free_ids_;

libs/ecs/source/container.cpp

@@ -116,6 +116,11 @@ namespace psemek::ecs
 		}
 	}
 
+	std::size_t container::entity_count()
+	{
+		return entity_list_.size();
+	}
+
 	std::size_t container::cache_count()
 	{
 		return query_cache_container_.cache_count();