/** Returns a stable Promise for when we're mounted, suitable for passing down to child components.
* @example
 * ```
* const Child = ({ parentMounted }) => {
*   useWhileMounted(() => {
*      parentMounted.then(() => ...)
*   })
* }
 
* const Parent = () => {
*   const myMountEvent = useMyMountEvent();
*   return <Child parentMounted={myMountEvent}/>
* ```
*/
export declare function useMyMountEvent(): Promise<void>;