minor language additions and css adjustments

Signed-off-by: Michael Kaufmann <d00p@froxlor.org>

lib/formfields/admin/messages/formfield.messages_add.php

@@ -49,6 +49,11 @@ return [
 					]
 				]
 			]
+		],
+		'buttons' => [
+			[
+				'label' => lng('admin.message')
+			]
 		]
 	]
 ];