function add_legacy_event_listener($$props, event_name, event_callback) {
	$$props.$$events ||= {};
	$$props.$$events[event_name] ||= [];
	$$props.$$events[event_name].push(event_callback);
}
Used to simulate `$on` on a component instance when `compatibility.componentApi === 4`
@param {Record<string, any>} $$props
@param {string} event_name
@param {Function} event_callback