Expose "reset" color value in themes

[chtenb]

The Color struct has a Reset value, which should reset the color to the default terminal foreground or background. But this doesn't seem to be exposed to be used in themes, as far as I could find anyway.

Being able to access the default fg/bg colors in a theme is useful, because they may differ from the 16 colors/256 colors in the terminal color palette. In curses, the default color can be called with the number -1, while the colors are called with numbers 0..255. I have no preference if helix should expose it like this or rather something else.

[the-mikedavis]

I believe we just need to add reset.to_string() => Color::Reset to the default palette:

helix/helix-view/src/theme.rs

Lines 358 to 381 in aeaeb09

	impl Default for ThemePalette {
	fn default() -> Self {
	Self {
	palette: hashmap! {
	"black".to_string() => Color::Black,
	"red".to_string() => Color::Red,
	"green".to_string() => Color::Green,
	"yellow".to_string() => Color::Yellow,
	"blue".to_string() => Color::Blue,
	"magenta".to_string() => Color::Magenta,
	"cyan".to_string() => Color::Cyan,
	"gray".to_string() => Color::Gray,
	"light-red".to_string() => Color::LightRed,
	"light-green".to_string() => Color::LightGreen,
	"light-yellow".to_string() => Color::LightYellow,
	"light-blue".to_string() => Color::LightBlue,
	"light-magenta".to_string() => Color::LightMagenta,
	"light-cyan".to_string() => Color::LightCyan,
	"light-gray".to_string() => Color::LightGray,
	"white".to_string() => Color::White,
	},
	}
	}
	}

(plus add it to the theme docs)