Update some options for pagination

DEVELOPER_GUIDE.md

@@ -65,6 +65,8 @@ It is difficult to describe by text. So please see below figure:
 * **OptionDescriptionBGColor(prompt.Color)** : default `prompt.Turquoise`
 * **OptionSelectedDescriptionTextColor(prompt.Color)** : default `prompt.White`
 * **OptionSelectedDescriptionBGColor(prompt.Color)** : default `prompt.Cyan`
+* **OptionScrollbarThumbColor** : `prompt.DarkGray`
+* **OptionScrollbarBGColor** : `prompt.Cyan`
 
 **Other Options**
 
@@ -77,6 +79,9 @@ Option to set history.
 #### `OptionPrefix(string)` : default `"> "`
 Option to set prefix string.
 
+#### `OptionLivePrefix(func() (prefix string, useLivePrefix bool))` : default `nil`
+Option to set a callback function for updating prefix string dynamically.
+
 #### `OptionMaxSuggestions(x uint16)` : default `6`
 The max number of displayed suggestions.
 

option.go

@@ -142,6 +142,20 @@ func OptionSelectedDescriptionBGColor(x Color) Option {
 	}
 }
 
+func OptionScrollbarThumbColor(x Color) Option {
+	return func(p *Prompt) error {
+		p.renderer.scrollbarThumbColor = x
+		return nil
+	}
+}
+
+func OptionScrollbarBGColor(x Color) Option {
+	return func(p *Prompt) error {
+		p.renderer.scrollbarBGColor = x
+		return nil
+	}
+}
+
 // OptionMaxSuggestion specify the max number of displayed suggestions.
 func OptionMaxSuggestion(x uint16) Option {
 	return func(p *Prompt) error {