adding .png image format req

aireilly · aireilly · commit 3254bf0ccd79 · 2022-09-19T10:24:31.000+01:00
diff --git a/contributing_to_docs/doc_guidelines.adoc b/contributing_to_docs/doc_guidelines.adoc
@@ -835,6 +835,10 @@ If a documentation change is due to a Bugzilla bug or Jira issue, the bug/issue
 
 == Images
 
+=== Image format
+
+Use `*.png` format images.
+
 === Block images
 
 To include a block image (an image on its own line):
