Add color variable used for unselected subtitle

[RandomSeeded]

Is your feature request related to a problem? Please describe.
I find it very difficult to make out the text for unselected subtitles - here's a screenshot which demonstrates the very faint subtitle

I'm hoping to increase the contrast

Describe the solution you'd like
It looks like this color is not configurable (according to

nap/style.go

Line 94 in 4f83f8e

UnselectedSubtitle: lipgloss.NewStyle().Foreground(lipgloss.Color("237")),

- it looks like it's hardcoded) - ideally this color would be configurable as well :)

Describe alternatives you've considered
(n/a)

Additional context
(n/a)