chore: add missing export (#1047)

[![PR App][icn]][demo] | Fix RM-XYZ
:-------------------:|:----------:

## 🧰 Changes
- I forgot to actually export the new `exports` util oops 

## 🧬 QA & Testing

- [Broken on production][prod].
- [Working in this PR app][demo].


[demo]: https://markdown-pr-PR_NUMBER.herokuapp.com
[prod]: https://SUBDOMAIN.readme.io
[icn]:
https://user-images.githubusercontent.com/886627/160426047-1bee9488-305a-4145-bb2b-09d8b757d38a.svg

index.tsx

@@ -13,5 +13,5 @@ const utils = {
   calloutIcons: {},
 };
 
-export { compile, hast, run, mdast, mdastV6, mdx, migrate, plain, remarkPlugins, tags } from './lib';
+export { compile, exports, hast, run, mdast, mdastV6, mdx, migrate, plain, remarkPlugins, tags } from './lib';
 export { Components, utils };