Make it compatible with Hugo 0.55 (#13680)

This commit adds two backwards compatible changes to prepare for the next Hugo version, most notable:

* All the `File` methods on `Page` has been deprecated and will give a warning in the next Hugo version. Adjust this by changing `.Dir` to ´.File.Dir` and similar.
* Version the capture shortcode to use the old behaviour for markdown rendering of shortcode inner content.

layouts/docs/list.html

@@ -1,5 +1,11 @@
 {{ define "content" }}
-	 {{ with .Content }}
+    {{ $hasContent := false }}
+    {{ with .File }}
+    {{ if ne .Filename "" }}
+    {{ $hasContent =  (ge (len $.RawContent) 100) }}
+    {{ end }}
+    {{ end }}
+	 {{ if $hasContent }}
 	 {{ partial "docs/content-page" (dict "ctx" $ "page" $ ) }}
 	 {{ else }}
     {{ if ge (len .Pages) 1 }}