update config (goldmark.extensions)

adds extra extension but has to disable strikethrough extension
(extra includes strikethrough)

config/_default/markup.toml

@@ -3,19 +3,25 @@
 
 # let us put inline html into the markdown files
 [goldmark]
-[goldmark.renderer]
+  [goldmark.extensions]
+    strikethrough = false
+    [goldmark.extensions.extras]
+      [goldmark.extensions.extras.delete]
+        enable = true
+      [goldmark.extensions.extras.subscript]
+        enable = true
+  [goldmark.renderer]
     unsafe = true
 
-# use {.[css-class]} after a paragraph to apply styling
-[goldmark.parser]
-[goldmark.parser.attribute]
+  # use {.[css-class]} after a paragraph to apply styling
+  [goldmark.parser]
+  [goldmark.parser.attribute]
     block = true
 
-# let the theme styling apply for code blocks
-[highlight]
+  # let the theme styling apply for code blocks
+  [highlight]
     noClasses = false
 
-[tableOfContents]
+  [tableOfContents]
     startLevel = 2
     endLevel = 4
-