Add optional descriptions to attachments for context

Currently a lot of attachments are just like on Discord. No context. The problem is that some people who might join a group chat or a conversation late won't understand what's going on. This would require re-explaining everything.

A nice addition would be an "optional" attachment description, whether this is for images, files,... This could also help reports since maybe there's some context that's been missed.

A nice way to look at it is Reddit, but there's also design flaws on there related to this feature.