Function add_callback

RedEdrShared/loguru.cpp:934–945

	}

	void add_callback(
		const char* id,
		log_handler_t   callback,
		void* user_data,
		Verbosity       verbosity,
		close_handler_t on_close,
		flush_handler_t on_flush)
	{
		std::lock_guard<std::recursive_mutex> lock(s_mutex);
		s_callbacks.push_back(Callback{ id, callback, user_data, verbosity, on_close, on_flush, 0 });
		on_callback_change();
	}

	// Returns a custom verbosity name if one is available, or nullptr.
	// See also set_verbosity_to_name_callback.