Bottom toolbar

I have just switched from my own code to this contrib and I I found an issue.

For the bottom toolbar to have the expected colour s from starship you need to add
```
$XONSH_STYLE_OVERRIDES['bottom-toolbar'] = 'noreverse'
```

as something in prompt-toolkit or xonsh, I think the former messes around with the colours. I had discussions on this years ago but can't find them now. (GitHub search is broken for xonsh)

To reproduce just point $XONTRIB_PROMPT_STARSHIP_BOTTOM_CONFIG to your normal starship config and see the difference.