message: Allow extensions on Nunjucks
diff: @@ -14,6 +14,11 @@ export default function (userOptions) {
  return (site) => {
  const nunjucksEngine = new NunjucksEngine(site, options.options);
  + const nunjucksExtensions = options.options.extensions ?? {};
  + for (const name of Object.keys(nunjucksExtensions)) {
  + nunjucksEngine.engine.addExtension(name, nunjucksExtensions[name]);
  + }
  +
  site.loadPages(options.extensions, loader, nunjucksEngine);
  site.filter("njk", filter, true);
  