Add an `{image}` role for inline images

[choldgraf]

MyST has a block-level {image} directive, which lets you control things like class, alt, width etc, and also lets you use inline attributes syntax like {image .my-class}. But there is no inline equivalent! This means that users who want non-basic functionality for in-line images don't have a way to do so.

We should enable authors to do things like:

This image {image alt="My alt" .inline-icon}`./image.png` is pretty neat!

We could essentially mimic the functionality of the {image} directive (maybe removing things like width/height and capping the height to 1.1rem or something.

Related

• Adding CSS Classes to Inline images (or disabling optimizations) #2839 - would resolve this
• Images that are inline with text #583 (this might help us avoid confusion that PRs like this have to make assumptions around, since we could emit a myst-inline-image class or something)

[rowanc1]

Nice. I like this direction of having role-equivalents of markdown functions.

This could be extended to links, strong, emphasis as well, which then gives the ability to add classes and IDs or other attributes, which currently we don't have a way to tag a link etc.

[cycomachead]

One other advantage here, related to accessibility:

We should distinguish between alt="" and no alt provided or even just alt without an empty string.
I've been able to write some simple image roles for my case: https://github.com/snap-cloud/manual/blob/main/_support/plugins/img-role.mjs#L10

The one thing, I didn't do (properly) yet, is handle alt text. required: true fails on the empty, but an empty alt text is explicitly one way to declare an image is presentational to a screen reader.

The other thing in that file is pure opinion: I've been using an image role (rather than the directive) for block images. In part, getting the find-and-replace logic in adapting this book was easier w/ a role. Otherwise, I think I like the slightly less 'weighty' syntax for a book that has many many images.