docs: Prepare for new sub tree

See #11925

docs/content/en/contribute/_index.md

@@ -1,16 +0,0 @@
----
-title: Contribute to the Hugo project
-linkTitle: Overview
-description: Contribute to Hugo development, documentation, and themes.
-categories: []
-keywords: []
-menu:
-  docs:
-    identifier: contribute-overview
-    parent: contribute
-    weight: 10
-weight: 10
-aliases: [/tutorials/how-to-contribute-to-hugo/,/community/contributing/]
----
-
-Hugo relies heavily on the enthusiasm and participation of the open-source community. We need your support.