docs: Prepare for new sub tree

See #11925

docs/content/en/functions/encoding/Base64Decode.md

@@ -1,40 +0,0 @@
----
-title: encoding.Base64Decode
-description: Returns the base64 decoding of the given content.
-categories: []
-keywords: []
-action:
-  aliases: [base64Decode]
-  related:
-    - functions/encoding/Base64Encode
-  returnType: string
-  signatures: [encoding.Base64Decode INPUT]
-aliases: [/functions/base64Decode]
----
-
-```go-html-template
-{{ "SHVnbw==" | base64Decode }} → Hugo
-```
-
-Use the `base64Decode` function to decode responses from APIs. For example, the result of this call to GitHub's API contains the base64-encoded representation of the repository's README file:
-
-```text
-https://api.github.com/repos/gohugoio/hugo/readme
-```
-
-To retrieve and render the content:
-
-```go-html-template
-{{ $u := "https://api.github.com/repos/gohugoio/hugo/readme" }}
-{{ with resources.GetRemote $u }}
-  {{ with .Err }}
-    {{ errorf "%s" . }}
-  {{ else }}
-    {{ with . | transform.Unmarshal }}
-      {{ .content | base64Decode | markdownify }}
-    {{ end }}
-  {{ end }}
-{{ else }}
-  {{ errorf "Unable to get remote resource %q" $u }}
-{{ end }}
-```