Introduce Core Widget: Image

[melchoyce]

This ticket introduces a new core widget for displaying images.

See 32417#comment:136 for history.

Keep an eye on ​https://github.com/xwp/wp-core-media-widgets for development.

An initial version of the image widget is available now for testing as part of the Core Media Widgets feature plugin: ​https://wordpress.org/plugins/wp-core-media-widgets/

Please report issues and feedback on the GitHub project: ​https://github.com/xwp/wp-core-media-widgets/issues

In 40640:

Widgets: Introduce media widgets for images, audio, and video with extensible base for additional media widgets in the future.

The last time a new widget was introduced, Vuvuzelas were a thing, Angry Birds started taking over phones, and WordPress stopped shipping with Kubrick. Seven years and 17 releases without new widgets have been enough, time to spice up your sidebar!

Props westonruter, melchoyce, obenland, timmydcrawford, adamsilverstein, gonom9, wonderboymusic, Fab1en, DrewAPicture, sirbrillig, joen, matias, samikeijonen, afercia, celloexpressions, designsimply, michelleweber, ranh, kjellr, karmatosed.
Fixes #32417, #39993, #39994, #39995.

In 40670:

Widgets: Prevent image title attribute from being populated from attachment title by default upon selection.

Props westonruter, timmydcrawford.
See #39993.

In 40812:

Widgets: clarify some context information for translators.

Props Italian polyglots team.
Amends [40640].
See #32417, #39993, #39994, #39995.

In 41252:

Widgets: Expose link URL input field in Image widget to avoid having to open media modal to discover.

Props timmydcrawford, westonruter.
See #39993.
Fixes #41274.

In 41549:

Widgets: Omit attributes from an Image widget's link when they are empty.

Props subrataemfluence, Nenad Obradovic, westonruter.
See #39993.
Fixes #41919.