TODO:
- [x] Add markdown rendering to channel chat
- [x] Unify (?) rendering logic between hover popover and chat
- [x] ~~Determine how to deal with document-oriented markdown like `#`~~
Unimportant until we want to do something special with `#channel`
- [x] Tidy up spacing and styles in chat panel

Release Notes:

- Added markdown rendering to channel chat
- Improved channel chat message style
- Fixed a bug where long chat messages would not soft wrap