Wrap section header extra content under the header

Make the extra content for section headers flow under the heading when
there is not enough space to show both the heading and the extra content
in a single line.

packages/web_ui/src/index.css

@@ -73,6 +73,7 @@ body {
 
 .section-header {
 	display: flex;
+	flex-wrap: wrap;
 	align-items: center;
 	margin-top: 16px;
 	margin-bottom: 8px;