Add custom headline style support

Add `HeadlineStyle` function to apply a custom style to the headline.

Author: HeavyWombat

box.go

@@ -34,8 +34,9 @@ import (
 type BoxStyle func(*boxOptions)
 
 type boxOptions struct {
-	headlineColor *colorful.Color
-	contentColor  *colorful.Color
+	headlineColor  *colorful.Color
+	contentColor   *colorful.Color
+	headlineStyles []bunt.StyleOption
 }
 
 // HeadlineColor sets the color of the headline text
@@ -45,6 +46,13 @@ func HeadlineColor(color colorful.Color) BoxStyle {
 	}
 }
 
+// HeadlineStyle sets the style to be used for the headline text
+func HeadlineStyle(style bunt.StyleOption) BoxStyle {
+	return func(options *boxOptions) {
+		options.headlineStyles = append(options.headlineStyles, style)
+	}
+}
+
 // ContentColor sets the color of the content text
 func ContentColor(color colorful.Color) BoxStyle {
 	return func(options *boxOptions) {
@@ -87,6 +95,10 @@ func ContentBox(headline string, content string, opts ...BoxStyle) string {
 		}
 	}
 
+	for _, style := range options.headlineStyles {
+		headline = bunt.Style(headline, style)
+	}
+
 	var buf buntBuffer
 	buf.Write("%s %s\n", beginning, headline)
 

box_test.go

@@ -58,6 +58,32 @@ content
 `)))
 		})
 
+		It("should create a simply styled content box with bold headline", func() {
+			Expect("\n" + ContentBox(headline, content,
+				HeadlineStyle(Bold()),
+			)).To(BeEquivalentTo(Sprintf(`
+╭ *headline*
+│ multi
+│ line
+│ content
+╵
+`)))
+		})
+
+		It("should create a simply styled content box with italic, underline, and bold headline", func() {
+			Expect("\n" + ContentBox(headline, content,
+				HeadlineStyle(Italic()),
+				HeadlineStyle(Underline()),
+				HeadlineStyle(Bold()),
+			)).To(BeEquivalentTo(Sprintf(`
+╭ _*~headline~*_
+│ multi
+│ line
+│ content
+╵
+`)))
+		})
+
 		It("should create styled content box with headline colors", func() {
 			Expect("\n" + ContentBox(headline, content,
 				HeadlineColor(DodgerBlue),