function remarkParse(options) {
  const self = this

  /**
   * @param {string} document
   * @returns {Root}
   */
  self.parser = function (document) {
    return fromMarkdown(document, {
      ...self.data('settings'),
      ...options,
      // Note: these options are not in the readme.
      // The goal is for them to be set by plugins on `data` instead of being
      // passed by users.
      extensions: self.data('micromarkExtensions') || [],
      mdastExtensions: self.data('fromMarkdownExtensions') || []
    })
  }
}
Aadd support for parsing from markdown.

@this {Processor<Root>}
  Processor instance.
@param {Readonly<Options> | null | undefined} [options]
  Configuration (optional).
@returns {undefined}
  Nothing.