message: Export hljs object
  Ability to register languages is missing without it. Workaround is to import the dependency manually, but urgh..
diff: import hljs, { HighlightOptions } from "../deps/highlight.ts";
  import { merge } from "../core/utils.ts";
  +export { hljs };
  +
  import type { Page, Site } from "../core.ts";
  export interface Options {
  