Styling configuration support

Currently, there is a barebones system for styling in configs, however, we do not make use of the provided config anywhere. It is also somewhat limited, and I would like to have truecolor support as well, since a lot of terminals support it now.

There are a few challenges for this, though:
- We use `crossterm` as the ratatui backend with our own SSH stream implementation; see https://github.com/ratatui/ratatui/issues/475
- It is possible some crates might try to query the terminal emulator for truecolor capabilities, which won't work over SSH
- How should the default color palette look? Should we allow multiple palettes with a interactive selection menu at runtime?