feat: add a Styler interface for styling bubbles

This change introduces a Styler interface that allows users to define
custom styles for bubbles. The interface is implemented by the StylerFunc
type, which is a function type that takes a boolean argument and returns
a value of any type.

This allows a user to define a custom StylerFunc that returns a custom
style for a bubble based on the background color of the terminal.

help/help.go

@@ -41,7 +41,8 @@ type Styles struct {
 	FullSeparator lipgloss.Style
 }
 
-func newStyles(isDark bool) Styles {
+// DefaultStyles returns a set of default styles for the help bubble.
+func DefaultStyles(isDark bool) Styles {
 	lightDark := lipgloss.LightDark(isDark)
 
 	keyStyle := lipgloss.NewStyle().Foreground(lightDark("#909090", "#626262"))
@@ -59,16 +60,6 @@ func newStyles(isDark bool) Styles {
 	}
 }
 
-// DefaultDarkStyles returns a set of default styles for dark backgrounds.
-func DefaultDarkStyles() Styles {
-	return newStyles(true)
-}
-
-// DefaultLightStyles returns a set of default styles for light backgrounds.
-func DefaultLightStyles() Styles {
-	return newStyles(false)
-}
-
 // Model contains the state of the help view.
 type Model struct {
 	Width   int
@@ -85,12 +76,12 @@ type Model struct {
 }
 
 // New creates a new help view with some useful defaults.
-func New() Model {
+func New(isDark bool) Model {
 	return Model{
 		ShortSeparator: " • ",
 		FullSeparator:  "    ",
 		Ellipsis:       "…",
-		Styles:         DefaultDarkStyles(),
+		Styles:         DefaultStyles(isDark),
 	}
 }
 

help/help_test.go

@@ -10,7 +10,7 @@ import (
 )
 
 func TestFullHelp(t *testing.T) {
-	m := New()
+	m := New(true)
 	m.FullSeparator = " | "
 	k := key.WithKeys("x")
 	kb := [][]key.Binding{