docs: Prepare for new sub tree

See #11925

docs/config/_default/markup.toml

@@ -1,31 +0,0 @@
-defaultMarkdownHandler = "goldmark"
-
-[goldmark]
-[goldmark.extensions]
-definitionList = true
-footnote = true
-linkify = true
-strikethrough = true
-table = true
-taskList = true
-typographer = true
-[goldmark.parser]
-autoHeadingID = true
-autoHeadingIDType = "github"
-[goldmark.parser.attribute]
-block = true
-title = true
-[goldmark.renderer]
-hardWraps = false
-unsafe = false
-xhtml = false
-
-[highlight]
-style = "trac"
-lineNumbersInTable = true
-noClasses = false
-
-[tableOfContents]
-endLevel = 2
-ordered = false
-startLevel = 2