Implement menu for KebabHorizontalIcon

[laymonage]

Right now, the KebabHorizontalIcon is there just as a placeholder. We'll need to implement this, eventually.

GitHub:

I think we only need the "Copy link" and "Quote reply" menu items. For "Hide" and "Delete", I don't know if it's worth the effort. For "Edit", it would be awesome, but I imagine it wouldn't be so easy to implement. The thing is, if users really need to "Edit", "Hide", and "Delete" (or even "Report content"), they can always jump on GitHub 😆

[laymonage]

I've temporarily hidden the icon until this is resolved.

[expikr]

Perhaps a placeholder "Edit on GitHub" link could be used as a stopgap measure in the meantime?

[JiayinCao]

Does anyone have any insight about the latest progress of this feature request?

It would be quite useful to have such a menu so that we can

• edit messages
• delete messages
• share link

Even though it is likely most Github users would know how to use the Githut disucssion system, in an ideal world, they don't need to know it is Github Discussion that is behind giscus.