(Accessibility) Implement alt text analogue for videos

[qweertz]

Requirements

• This is a feature request and not a bug report. Otherwise, please create a new bug report instead.
• Please check to see if this request (or a similar one) already exists.
• It's a single feature. Please don't request multiple features in one issue.

Describe the feature you'd like

It would be nice to have the ability to add descriptive text to videos in a similar way to adding alt text to image posts. And for that text to be accessible to screen readers without cluttering the body of a post. This would bring all the benefits of the alt text function already present for image posts.

I am aware that, unlike <img>, <video> does not have an alt attribute. However, from my understanding, the aria-label attribute would do essentially the same thing.

---

Related question: If this were to be implemented, would it make sense to also add the separate ability to provide files in the WebVTT format (.vtt) to be used through the <track> tag? This would enable ppl to:

specify a timed text track (or time-based data) that can be displayed in parallel with the media element, for example to overlay subtitles or closed captions on top of a video or alongside audio tracks.
(taken from the MDN web docs)

This can be used to provide subtitles, captions, or chapters.