docs: Prepare for new sub tree

See #11925

docs/content/en/functions/resources/Concat.md

@@ -1,26 +0,0 @@
----
-title: resources.Concat
-description: Returns a concatenated slice of resources.
-categories: []
-keywords: []
-action:
-  aliases: []
-  related: []
-  returnType: resource.Resource
-  signatures: ['resources.Concat TARGETPATH [RESOURCE...]']
----
-
-The `resources.Concat` function returns a concatenated slice of resources, caching the result using the target path as its cache key. Each resource must have the same [media type].
-
-Hugo publishes the resource to the target path when you call its [`Publish`], [`Permalink`], or [`RelPermalink`] methods. 
-
-[media type]: https://en.wikipedia.org/wiki/Media_type
-[`publish`]: /methods/resource/publish
-[`permalink`]: /methods/resource/permalink
-[`relpermalink`]: /methods/resource/relpermalink
-
-```go-html-template
-{{ $plugins := resources.Get "js/plugins.js" }}
-{{ $global := resources.Get "js/global.js" }}
-{{ $js := slice $plugins $global | resources.Concat "js/bundle.js" }}
-```