add image description to NoteAttachment

[Marzal]

Some Fediverse instances won't show the images of a toot/message if not ALT text is given.

I would rather have a more verbose description like:

Artwork from the $episode, more info in $episode_web_URL

but given what I've seen already in the code this is what I can write (without been a developer)

Not tested, and first time reading rust code, so probably this would crash the server.
Let's call this an issue+ more than a real PR

[qazmlp]

I suspect that if an instance has an automated rule against images without alt text, they'd also moderate against consistently unhelpful alt text, so this circumvention likely isn't useful.

(I have a hunch an unhelpful automated description might be a worse experience for screen reader users than no description at all, too, but I could be mistaken about that.)

[Marzal]

As far as I know it's recommended to put a null character in the alt text if the image is not relevant, so the screen reader knows that the "alt text" is not missing/ forgotten to be introduced

https://www.w3.org/WAI/tutorials/images/decorative/

Given that this is for occasional toots in the timeline, I think that is better to know that the image shown is the official logo of the podcast rather than not know anything, and giving the opportunity to the user to go to the official website and see if there is a description if they are interested.

I would bet that a high % of instances would allow this, rather than active banning this use case. With the result of a lot of clients displaying the image without problem.

PD: I think that one way to make more useful the image tag could be to add and optional attribute for the alt text
https://github.com/Podcastindex-org/podcast-namespace/blob/main/docs/1.0.md#images