Semantic elements for non-link links: async-upload.php

[Cheffheid]

The "Dismiss" link that appears when an error occurs during the upload should be a button instead.

Related: #26504, #35126

[Cheffheid]

markup update, no style changes

[Cheffheid]

markup update, minimal style updates (positioning)

[Cheffheid]

I'm dumb. Ignore the first patch, minimal style changes are needed to reposition the button to its correct place.

[Cheffheid]

Markup update, full styles update

[Cheffheid]

To clarify, because I've made such a mess of these patches, I've uploaded two patches that work:

38671.4.patch: Assumes button-link will do all the work (and it should when #35126 goes through)
38671.5.patch: Includes styles to make the button look like a link, in case #35126 takes longer than expected/takes a different direction/whatever.

[Cheffheid]

Markup update, full styles update (for reals)

[Cheffheid]

markup update, minimal style updates (positioning)

[Cheffheid]

Markup update, full styles update (for reals)

[afercia]

Moving to 5.0 for testing and visibility. A screenshot to clarify to everyone where this button is would be welcome :)

[audrasjb]

Hello,

To clarify a bit what happens, here are the few steps to reproduce the issue:

• Go to wp-admin/media-new.php, then upload a file with a not supported MIME type.
• The alert have a "Dismiss" link and it should be a button HTML element.

The patch works, however a type="button" attribute is needed because this button is not related to a form or whatever.
See ​https://developer.mozilla.org/en-US/docs/Web/HTML/Element/button#attr-type for further documentation.

[audrasjb]

Screenshot for this issue.

[audrasjb]

Adds type="button" attribute and removes two extra spaces in CSS

[afercia]

Reviewng last patch, there's no need for all the textra styling, the CSS class button-link already takes care of the necessary styling. Will remove during commit.

[afercia]

In 42784:

Accessibility: Change the media upload "Dismiss error" link to a button.

For better accessibility and semantics, user interface controls that perform an
action should be buttons. Links should exclusively be used for navigation.

Props Cheffheid, audrasjb.
Fixes #38671.