/**
 * Map OOXML underline types to CSS text-decoration properties.
 * Returns a CSS style string (kebab-case) suitable for inline decorations.
 *
 * @param {Object} params
 * @param {string} [params.type='single'] - OOXML w:u@w:val value
 * @param {string|null} [params.color=null] - CSS color (e.g., '#RRGGBB')
 * @param {string|null} [params.thickness=null] - Optional explicit thickness (e.g., '0.2em', '2px')
 * @param {boolean} [params.approximate=true] - Whether to approximate non-standard styles
 * @returns {string} CSS style string (e.g., 'text-decoration-line: underline; text-decoration-style: dashed;')
 */
export function getUnderlineCssString({ type, color, thickness, approximate }?: {
    type?: string;
    color?: string | null;
    thickness?: string | null;
    approximate?: boolean;
}): string;
