Update archetypes for taxonomies

archetypes/tags/_index.md

@@ -2,7 +2,14 @@
 
 title: {{ replace .Name "-" " " | title }}
 
-description: >-
-  A description of what the tag is.
-
 ---
+
+A short summary of what the tag is.
+
+<!--more-->
+
+Optionally provide more information about the tag here. This part will only show
+on the tag page, not on the tags list page.
+
+If you delete this section, DO NOT delete the summary separator (`<!--more-->`)
+or else the summary won't be shown.