static normalizeGlobalStyles(context, styles) {
        // Backwards compat with existing Vue globalStyles:
        // A string only is supported for sass / scss.
        if (typeof styles !== 'object') {
            styles = {
                sass: styles,
                scss: styles
            };
        }

        return mapValues(styles, files => {
            files = concat([], files);

            return files.map(file => context.paths.root(file));
        });
    }
@param {import('../Mix')} context
@param {string | Record<string, string|string[]>} styles