Status icons need alternative text

Issue Summary

There are a number of icons in the CMS which don’t come with alternative text, even though their presence in the UI greatly changes the meaning of the surrounding content. Here are two examples.

In concurrent editing notifications, we use the red color and "warning" icon to indicate that there is a risk of destructive action / the message warrants attention. I think the message next to the icon isn’t enough to convey the same information for screen reader users. Adding "Warning" as alt text for the image would help quite a bit.

For Validation errors in forms, we also use the same icons. Here the wording of the message helps quite a bit more, but it feels to me like also adding "Warning" as alt text would help disambiguate a validation error from help text.

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I think the same rationale also applies to help blocks and status banners / messages with "success", "error", "info", "warning" styles.

Working on this

Anyone can contribute to this. The first step will be to discuss whether there is indeed an issue here, and if so, come up with a plan + appropriate alt text to use. View our contributing guidelines, add a comment to the issue once you’re ready to start.