Merge branch 'calebw-master-patch-38960' into 'master'

Clarify linking Wiki pages in asciidoc format

See merge request gitlab-org/gitlab!80325

doc/user/asciidoc.md

@@ -232,6 +232,11 @@ v1.0, 2019-01-01
 
 #### Includes
 
+NOTE:
+[Wiki pages](project/wiki/index.md#create-a-new-wiki-page) created with the AsciiDoc
+format are saved with the file extension `.asciidoc`. When working with AsciiDoc wiki
+pages, change the file name from `.adoc` to `.asciidoc`.
+
 ```plaintext
 include::basics.adoc[]