Adds header (#6842) (#6844)

(cherry picked from commit 86baa86)

Co-authored-by: Nastasha Solomon <[email protected]>

Author: mergify[bot]

docs/release-notes/8.18.asciidoc

@@ -5,6 +5,10 @@
 [[release-notes-8.18.1]]
 === 8.18.1
 
+[discrete]
+[[known-issue-8.18.1]]
+==== Known issues
+
 // tag::known-issue[]
 [discrete]
 .The technical preview badge incorrectly displays on the alert suppression fields for event correlation rules