markup/goldmark: Add the Hugo Goldmark Extras "delete" extension

With Goldmark v1.7.1 and earlier, the Goldmark "strikethrough" extension was
triggered by wrapping text within a pair of double-tilde characters. With
Goldmark v1.7.2 and later, to provide full GFM compatibility, the Goldmark
"strikethrough" extension is triggered by wrapping text within a pair of
single- or double-tilde characters.

This change created a conflict with the Hugo Goldmark Extras "subscript"
extension.

When enabling the Hugo Goldmark Extras "subscript" extension, if you
want to render subscript and strikethrough text concurrently, you must:

1. Disable the Goldmark "strikethrough" extension
2. Enable the Hugo Goldmark Extras "delete" extension

Closes #12597

docs/data/docs.yaml

@@ -1082,6 +1082,8 @@ config:
           escapedSpace: false
         definitionList: true
         extras:
+          delete:
+            enable: false
           insert:
             enable: false
           mark:
@@ -1589,8 +1591,8 @@ config:
   paginate: 0
   paginatePath: ""
   pagination:
-    defaultPageSize: 10
     disableAliases: false
+    pagerSize: 10
     path: page
   panicOnWarning: false
   params: {}