message: Add details and summary to allowed HTML tags
  Implements MSC2184 (https://github.com/matrix-org/matrix-doc/pull/2184)
diff: @@ -237,6 +237,7 @@ const sanitizeHtmlParams: IExtendedSanitizeOptions = {
  'h1', 'h2', 'h3', 'h4', 'h5', 'h6', 'blockquote', 'p', 'a', 'ul', 'ol', 'sup', 'sub',
  'nl', 'li', 'b', 'i', 'u', 'strong', 'em', 'strike', 'code', 'hr', 'br', 'div',
  'table', 'thead', 'caption', 'tbody', 'tr', 'th', 'td', 'pre', 'span', 'img',
  + 'details', 'summary',
  ],
  allowedAttributes: {
  // custom ones first:
  