UI-tests und fixes aus tests

public/js/test/tests.js

@@ -28,6 +28,7 @@ import './editor.test.js';
 import './editor-features.test.js';
 import './editor-save.test.js';
 import './editor-toolbar.test.js';
+import './line-numbers.test.js';
 import './snippets.test.js';
 import './image-fullscreen.test.js';
 import './markdown.test.js';