Consider iterating text on media upload for alt text

[karmatosed]

This could be confusing both in what it does and linking to an external source. It might be a good idea to work on some ideas to improve the copy here and also linking.

[melchoyce]

Historical context in #41612

[hellofromTonya]

#51616 was marked as a duplicate.

[hellofromTonya]

Merging @garrett-eclipse description from a duplicate ticket #51616:

On Media Modals the Alt Text has a description containing a link 'Describe the purpose of the image.' that's a little misleading to new users. It feels less a description and information and more an action in that users click it thinking that's how one would describe the image but instead find it's just information.

Could a little (i) icon be added to denote it as informational. Or could we adjust the language;
_Alt Text_ describes the image purpose.
*Where just the 'Alt Text' part is links.
This i feel would take the link off the action word which is what currently makes the link feel like an action and not just extra information.

Love the concept of the feature just think we can remove the ambiguity of the link purpose.

[afercia]

Linking to the related issue and PR on the Gutenberg repo:
​https://github.com/WordPress/gutenberg/issues/19068
​https://github.com/WordPress/gutenberg/pull/26520

The key concepts the accessibility team want to communicate with this text and that were discussed on #41612 and related conversations on Slack are the the following 3 ones:

• The alt text describes the purpose of the image, it's not the image description. The image purpose can be very different from the image content depending on usage and context.
• The link points to a resource that explains this concept in detail: the W3C "alt decision tree"
• In most of the cases, images are purely decorative and don't need an alt text. The part "Leave empty if the image is purely decorative" is fundamental to communicate this concept to users as they tend to think they have to provide an alt text in all cases (which is wrong)

Improvements to the current text are welcome as long as these three points are cleaerly communicated. Proposal with minimal change:

[link]Learn how to describe the purpose of the imagelink. Leave empty if the image is purely decorative.

[sabernhardt]

both PHP instances: editing text and replacing link for a potentially localized WordPress.org resource

[sabernhardt]

GB19068 mentions using a WordPress.org resource for the tutorial, and I chose the ​Accessibility Handbook page. That includes links to the decision tree.

The patch also uses an internationalization function for the link. A support article may be easier to translate, if we could find or add one.

Of course, the block editor change(s) would need a separate patch/PR.

[antpb]

Noting from the Media meeting discussion on this, it was generally agreed that this patch should point to the existing W3C url and not a WordPress.org url.

With that change made this text enhancement should be good to go.

[sabernhardt]

text change only (in both PHP files)

<!-Trac ticket:
https://core.trac.wordpress.org/ticket/48939

String changes sometimes break in tests so just being extra certain we're good there. :)

[antpb]

In 52033:

Media: Adjust alt text info link text.

Previous messaging of this link was confusing given it went to an external source. This change describes more accurately that it will perform the action of taking you to the resource.

Props karmatosed, joedolson, melchoyce, hellofromTonya, afercia, sabernhardt, antpb.
Fixes #48939.