feat: support for railStyle prop to Slider component (#40942)

components/slider/index.en-US.md

@@ -31,7 +31,8 @@ To input a value in a range.
 | vertical | If true, the slider will be vertical | boolean | false |  |
 | onAfterChange | Fire when onmouseup is fired | (value) => void | - |  |
 | onChange | Callback function that is fired when the user changes the slider's value | (value) => void | - |  |
-| trackStyle | The style of slider track | CSSProperties | - |  |
+| trackStyle | The style of slider track (the active range) | CSSProperties | - |  |
+| railStyle | The style of slider rail (the background) | CSSProperties | - |  |
 | handleStyle | The style of slider handle | CSSProperties | - |  |
 
 ### range

components/slider/index.tsx

@@ -80,6 +80,7 @@ export interface SliderSingleProps extends SliderBaseProps {
   onAfterChange?: (value: number) => void;
   handleStyle?: React.CSSProperties;
   trackStyle?: React.CSSProperties;
+  railStyle?: React.CSSProperties;
 }
 
 export interface SliderRangeProps extends SliderBaseProps {
@@ -90,6 +91,7 @@ export interface SliderRangeProps extends SliderBaseProps {
   onAfterChange?: (value: [number, number]) => void;
   handleStyle?: React.CSSProperties[];
   trackStyle?: React.CSSProperties[];
+  railStyle?: React.CSSProperties;
 }
 
 interface SliderRange {