Internal: The demo should fit.

sample/index.html

@@ -5,7 +5,7 @@
 	<title>CKEditor 5 – document editor build – development sample</title>
 	<style>
 		body {
-			max-width: 800px;
+			max-width: 900px;
 			margin: 20px auto;
 		}
 	</style>