fix(core): update

ts/smartmarkdown.plugins.ts

@@ -1,8 +1,9 @@
 // third party remark
 import remark from 'remark';
+import remarkFrontmatter from 'remark-frontmatter';
 import remarkHtml from 'remark-html';
 
-export { remark, remarkHtml };
+export { remark, remarkFrontmatter, remarkHtml };
 
 // other third party stuff
 import turndown from 'turndown';