feat: apply startIndex props

Author: kim0jun

example/App.tsx

@@ -24,6 +24,7 @@ type SliderOptions = {
   loop: boolean;
   autoPlay: boolean;
   autoPlayDelay: number;
+  startIndex: number;
   navStyle: 1 | 2;
   navSize: number;
   navMargin: number;
@@ -39,6 +40,7 @@ const App: React.FC = () => {
     loop: true,
     autoPlay: true,
     autoPlayDelay: 2,
+    startIndex: 3,
     navStyle: 1,
     navSize: 50,
     navMargin: 30,
@@ -118,7 +120,7 @@ const App: React.FC = () => {
         loop={sliderOptions.loop}
         autoPlay={sliderOptions.autoPlay}
         autoPlayDelay={sliderOptions.autoPlayDelay}
-        startIndex={0}
+        startIndex={sliderOptions.startIndex}
         useGPURender={sliderOptions.useGPURender}
         navStyle={sliderOptions.navStyle}
         navSize={sliderOptions.navSize}
@@ -131,7 +133,7 @@ const App: React.FC = () => {
         onCompleteSlide={onCompleteSlide}
       />
 
-      <div style={{ margin: '10px' }}>{slideIndexText || `${1} / ${IMAGES.length}`}</div>
+      <div style={{ margin: '10px' }}>{slideIndexText || `${sliderOptions.startIndex + 1} / ${IMAGES.length}`}</div>
 
       <List
         subheader={

src/ImageSlider.tsx

@@ -67,8 +67,12 @@ const SimpleImageSlider: React.FC<SimpleImageSliderProps> = ({
     autoPlay,
     autoPlayDelay: autoPlayDelay + slideDuration
   });
-  const [currentSliderStyle, setCurrentSlideStyle] = useState(styles.getImageSlide(getURLValueFromImages(images, 0), slideDuration, 0, useGPURender));
-  const [nextSliderStyle, setNextSliderStyle] = useState(styles.getImageSlide(getURLValueFromImages(images, 1), slideDuration, 1, useGPURender));
+  const [currentSliderStyle, setCurrentSlideStyle] = useState(
+    styles.getImageSlide(getURLValueFromImages(images, startIndex), slideDuration, 0, useGPURender)
+  );
+  const [nextSliderStyle, setNextSliderStyle] = useState(
+    styles.getImageSlide(getURLValueFromImages(images, startIndex + 1), slideDuration, 1, useGPURender)
+  );
   const isSlidingRef = useRef(false);
 
   const handleClick = useCallback(