/**
 * Returns a promise that waits for the browser to be back online.
 * Resolves to `true` if it it was offline before calling this function, `false` otherwise.
 * If a `signal` is provided, listens to it to cancel the promise.
 *
 * @param signal Optional signal parameter on which the `abort` event will be listened to.
 * @returns `true` if it it was offline before calling this function, `false` otherwise.
 */
export declare function untilOnline(signal?: AbortSignal): Promise<boolean>;