⚒️ Add optional category support for alt words. (#199)

* Add optional category support for alt words.

In the frontmatter for Markdown word definitions, the `alt_words` key
now supports any number of categories, though it functionally only
supports one level in the look & feel of the website.

If we wish to use multi-level categories, we can add a class to the <ul>
in order to cleanly style nested lists.

Resolves #170

* Fix: Digital Blackface lint issues.

11ty/definitions/dude.md

@@ -5,16 +5,18 @@ defined: true
 flag:
   level: avoid
 alt_words:
-  - wow
-  - oh my word
-  - yikes
-  - y'all
-  - friend
-  - mate
-  - fam
-  - folks
-  - pal*
-  - buddy*
+  expression of astonishment:
+    - wow
+    - oh my word
+    - yikes
+  noun:
+    - y'all
+    - friend
+    - mate
+    - fam
+    - folks
+    - pal*
+    - buddy*
 reading:
   - text: Etymonline entry
     href: https://www.etymonline.com/word/dude