Add quarto-assign (#1125) (#1126)

(cherry picked from commit 02e6336)

Co-authored-by: James J Balamuta <[email protected]>

docs/extensions/listings/shortcodes-and-filters.yml

@@ -396,4 +396,10 @@
   path: https://github.com/AndreasThinks/quarto-mastodon-comments
   author: "[AndreasThinks](https://github.com/AndreasThinks/)"
   description: |
-    Enables adding Mastodon powered comments to posts and articles.
+    Enables adding Mastodon powered comments to posts and articles.
+
+- name: assign
+  path: https://github.com/coatless-quarto/assign
+  author: "[James Joseph Balamuta](https://github.com/coatless/)"
+  description: |
+    A Quarto Extension for educators writing assignments by combining instruction and solution authoring.