Provide a way of changing the link target on media through ckeditor5

Problem/Motivation

When embedding a media item in ckeditor5 it is not possible to change the "target" attribute of the link, e.g. to set the link to open in a new window.

Proposed resolution

The link element for media items has a selector to indicate if the link should open in a new window.

Remaining tasks

Update the link widget.

User interface changes

The link element for media items has a selector to indicate if the link should open in a new window.

Introduced terminology

TBD

API changes

TBD

Data model changes

TBD

Release notes snippet

TBD