Rest client has untyped methods for some thread actions

[paperdave]

The following methods do not have types unless they are named something nonstandard.

• channel.listPublicArchivedThreads docs
• channel.listPrivateArchivedThreads docs
• channel.listJoinedPrivateArchivedThreads docs

I have an issue open upstream at discordjs/discord-api-types#526 inquiring about this. if enough time goes by, i'll take a deep look though api types and figure out how to implement them.

I would add the low hanging fruit tag but i don't think any action of touching gen-routes.js is low hanging haha.