Consider adding icons to featured images

> We can already change featured images by clicking on the post edit icon, but often when users want to change images, they'll try clicking on them directly. We could add icons to featured images also (example is the Edin front page):


Clicking on a featured image DM icon would open the editor in a new tab, and shake the featured image metabox.

Suggested by @kwight

Start by reproducing the featured-image interaction in the WordPress Customizer, using the Edin front page example and the existing post edit icon as reference. Check how featured images are edited and determine how a direct click should open the editor in a new tab and shake the featured-image metabox; done means both interactions work as described.

Written by the indexing model from the issue text.