/**
 * Rejects a promise if it does not settle within a specified duration.
 *
 * @example
 * await timeout(fetchData(), 5000, "Request timed out")
 *
 * @param promise The promise to wait for.
 * @param ms Maximum time to wait in milliseconds.
 * @param errorMessage Optional custom error message.
 * @returns The resolved value of the promise.
 */
export declare function timeout<T>(promise: Promise<T>, ms: number, errorMessage?: string): Promise<T>;