/**
 * Converts passed URL to its full form.
 * TODO: Maybe, there is a bit easier way? window.open will accept
 *  unformatted URL too, probably.
 *
 * @param url - URL to format.
 * @throws {Error} URL protocol is not supported by OS, or link has not allowed
 * protocol.
 * @private
 */
export declare function formatURL(url: string): string;