code: public static function demoteHtmlHeaderTags($html)
      {
          $originalHeaderTags = [];
          $demotedHeaderTags = [];
  
          foreach (range(100, 1) as $index) {
              $originalHeaderTags[] = '<h'.$index.'>';
  
              $originalHeaderTags[] = '</h'.$index.'>';
  
              $demotedHeaderTags[] = '<h'.($index + 1).'>';
  
              $demotedHeaderTags[] = '</h'.($index + 1).'>';
          }
  
          return str_ireplace($originalHeaderTags, $demotedHeaderTags, $html);
      }
docs: This function will demote H1 to H2, H2 to H3, H4 to H5, etc.
  this will help with SEO so there are not multiple H1 tags
  on the same page.
  
  @param HTML string
  
  @return HTML string