add background color and caption in code block

Signed-off-by: ariary <[email protected]>

block.go

@@ -402,6 +402,7 @@ func (i Image) GetURL() string {
 }
 
 type CodeBlock struct {
+	Caption []RichText `json:"caption,omitempty"`
 	BasicBlock
 	Code Code `json:"code"`
 }

const.go

@@ -89,16 +89,26 @@ const (
 )
 
 const (
-	ColorDefault Color = "default"
-	ColorGray    Color = "gray"
-	ColorBrown   Color = "brown"
-	ColorOrange  Color = "orange"
-	ColorYellow  Color = "yellow"
-	ColorGreen   Color = "green"
-	ColorBlue    Color = "blue"
-	ColorPurple  Color = "purple"
-	ColorPink    Color = "pink"
-	ColorRed     Color = "red"
+	ColorDefault           Color = "default"
+	ColorGray              Color = "gray"
+	ColorBrown             Color = "brown"
+	ColorOrange            Color = "orange"
+	ColorYellow            Color = "yellow"
+	ColorGreen             Color = "green"
+	ColorBlue              Color = "blue"
+	ColorPurple            Color = "purple"
+	ColorPink              Color = "pink"
+	ColorRed               Color = "red"
+	ColorDefaultBackground Color = "default_background"
+	ColorGrayBackground    Color = "gray_background"
+	ColorBrownBackground   Color = "brown_background"
+	ColorOrangeBackground  Color = "orange_background"
+	ColorYellowBackground  Color = "yellow_background"
+	ColorGreenBackground   Color = "green_background"
+	ColorBlueBackground    Color = "blue_background"
+	ColorPurpleBackground  Color = "purple_background"
+	ColorPinkBackground    Color = "pink_background"
+	ColorRedBackground     Color = "red_background"
 )
 
 const (