fix: enable wrapStandAloneImageWithinParagraph by default

This fixes invalid HTML where figure tag is inside p tag.
However, this does not fix linked images, e.g., `[![alt](image)](url)`.
The cleanest way to resolve linked images is using markdown-attributes,
but markdown-attributes is not recommended by CommonMark.

See:

- https://discourse.gohugo.io/t/how-to-do-wrap-img-with-a-inside-figure-with-render-image-html/44843
- https://github.com/gohugoio/hugo/blob/master/markup/goldmark/images/transform.go
- https://gohugo.io/content-management/markdown-attributes/
- https://github.com/commonmark/commonmark-spec/wiki/Deployed-Extensions#attributes

exampleSite/config/_default/markup.toml

@@ -2,6 +2,9 @@
 # These settings are required for the theme to function.
 
 [goldmark]
+  [goldmark.parser]
+    wrapStandAloneImageWithinParagraph = false
+
   [goldmark.renderer]
     unsafe = true