Announcement channels cannot be bridged

[FurblandChannel]

Announcement channels operate identically to normal Discord channels, but they can “publish” messages to other channels via a webhook. Due to the API version the bot uses, these channels cannot be bridged. It may be possible to allow the bot to treat them as normal channels and ignore the error, but they would have to be differentiated in some way from other unbridgeable channels (the discord API might return a different error message?).