Thread support

[TheDiscordian]

Discord, Slack, and Matrix support threads, so it might make sense for OneBot to support threads too.

[tippi-fifestarr]

I like this. What would it take to add this support?

[TheDiscordian]

@tippi-fifestarr the Message interface may need to be updated, not sure. It might make sense to have a Reply method to explicitly reply to a message, and the individual protocol plugins can handle themselves what a reply is. The closest we have to that rn is the Bluesky plugin, where the whole protocol is treated like one big room, and threads are effectively sub-rooms, so each post is a reply generally.