function combineHtmlExtensions(htmlExtensions) {
  /** @type {HtmlExtension} */
  const handlers = {}
  let index = -1

  while (++index < htmlExtensions.length) {
    htmlExtension(handlers, htmlExtensions[index])
  }

  return handlers
}
Combine multiple HTML extensions into one.

@param {ReadonlyArray<HtmlExtension>} htmlExtensions
  List of HTML extensions.
@returns {HtmlExtension}
  Single combined HTML extension.