Show alt/title text on long press of image

Checklist

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User Interface

Is your feature request related to a problem? Please describe.

Images often have alt text/title text describing the image for accessibility reasons, or an extra punchline in webcomic feeds. Currently there's no way to see this alt text in the app; you need to open the article in webview or your browser to long press the image and see the alt text there.

Describe the solution you'd like

I think the perfect solution would be to act exactly like the webview does: long press an image to get a context window that displays the alt text.

If easier to implement, there's already an expanded image view implemented, visible after selecting an image. And displaying the alt text as a caption at the bottom of this view would also be a good solution.

Related links

https://xkcd.com/atom.xml
https://qwantz.com/rssfeed.php
https://www.vox.com/rss/index.xml

Start by tracing the expanded image view and the image-selection flow in the Android app, then check how image alt/title text is retained from RSS content. Decide whether the long-press context window or a caption in the expanded view fits the existing UI, and verify that the text is visible for feeds such as xkcd and Qwantz.