/**
 * Decodes a Base64 encoded string to ASCII.
 *
 * @param base64String - The Base64 encoded string to decode.
 * @returns The decoded ASCII string.
 * @example
 * const decoded = fromBase64('SGVsbG8gV29ybGQ='); // 'Hello World'
 */
export declare function fromBase64(base64String?: string): string;