Merge branch 'document-how-to-add-comments' into 'master'

Describe how to add comments in the style guide

See merge request gitlab-org/gitlab!69601

doc/development/documentation/styleguide/index.md

@@ -443,6 +443,15 @@ When possible, try to avoid acronyms in headings.
   - List item 2
   ```
 
+### Comments
+
+To embed comments within Markdown, use standard HTML comments that are not rendered
+when published. Example:
+
+```html
+<!-- This is a comment that is not rendered -->
+```
+
 ### Emphasis
 
 - Use double asterisks (`**`) to mark a word or text in bold (`**bold**`).