### Todo

* [x] Add back chat functionality, connected to channels
* [x] Channels panel
* [x] channels with active calls take up two rows, facepile goes on the
second row
* [x] icons for note, phone, (maybe chat) appear on the right of channel
names
    * [x] clicking a channel opens the chat
    * [x] style
* [x] Chat panel
    * [ ] Render markdown in chat messages
    * [x] style
* [x] Hide unless user is staff or has `channels_alpha` feature flag.