code: function getPadding(source, html) {
    const re = new RegExp(`^([\\t ]+)${escape(source)}`, 'gm');
    const match = re.exec(html);
  
    return match ? match[1] : '';
  }
docs: Retrieve leading whitespace for 'source' in 'html'
  @param {String} source
  @param {String} html
  @returns {String}