### Markers integration [#643](https://github.com/ckeditor/ckeditor5-engine/issues/643)

1. Write before, after and inside marked text.
2. Remove before, after and inside marked text.
3. Make selection intersecting with marked text and remove it.
4. Make selection intersecting with marked text and start typing.
5. Style text and see if marked selection brakes in some way.
6. Click enter inside marked text.
7. Change a paragraph with marked text to a list item or header.
8. Remove all marked text and see if there are no artifacts.
9. Use undo.
10. Use buttons to create and remove markers.
11. Make different selections and play with "move to start" button.
