Slightly improve mentions

[micahmo]

Pull Request Description

This PR slightly improves mentions. There's probably more work that needs to go in there to make them more like replies (maybe just using CommentReference), but at least now the originating username follows standards from through the app.

Issue Being Fixed

Issue Number: N/A

Screenshots / Recordings

Before	After

Checklist

• Did you update CHANGELOG.md?
• Did you use localized strings where applicable?
• Did you add semanticLabels where applicable for accessibility?

[CTalvio]

This PR slightly improves mentions. There's probably more work that needs to go in there to make them more like replies (maybe just using CommentReference), but at least now the originating username follows standards from through the app.

Lemmy doesn't actually work with post body mentions, we could absolutely go ahead and just make mentions use the exact widgets that replies do.