Resolves #145: add particle offset (gapSize)

src/components/Carousel/Carousel.svelte

@@ -138,6 +138,14 @@
     data.particlesToScrollInit = particlesToScroll
   }
 
+  /**
+   * Size of gap between particles in px (pixels)
+   */
+  export let gapSize = 0
+  $: {
+    data.gapSize = gapSize
+  }
+
   export async function goTo(pageIndex, options) {
     const animated = get(options, 'animated', true)
     if (typeof pageIndex !== 'number') {
@@ -159,19 +167,18 @@
   let pageWindowWidth = 0
   let pageWindowElement
   let particlesContainer
+  let pageWindowElementResizeObserver
 
-  const pageWindowElementResizeObserver = createResizeObserver(({
-    width,
-  }) => {
-    pageWindowWidth = width
+const pageWindowElementResizeObserverHandler = ({ width }) => {
+    pageWindowWidth = width + data.gapSize
     data.particleWidth = pageWindowWidth / data.particlesToShow
 
     applyParticleSizes({
       particlesContainerChildren: particlesContainer.children,
-      particleWidth: data.particleWidth,
+      particleWidth: data.particleWidth - data.gapSize,
     })
     methods.offsetPage({ animated: false })
-  })
+  }
 
   function addClones() {
     const {
@@ -191,6 +198,7 @@
 
   onMount(() => {
     (async () => {
+      pageWindowElementResizeObserver = createResizeObserver(pageWindowElementResizeObserverHandler)
       await tick()
       if (particlesContainer && pageWindowElement) {
         data.particlesCountWithoutClones = particlesContainer.children.length
@@ -209,7 +217,9 @@
   })
 
   onDestroy(() => {
-    pageWindowElementResizeObserver.disconnect()
+    if (pageWindowElementResizeObserver) {
+      pageWindowElementResizeObserver.disconnect()
+    }
     progressManager.reset()
   })
 
@@ -286,6 +296,7 @@
         on:swipeFailed={handleSwipeFailed}
         on:swipeThresholdReached={handleSwipeThresholdReached}
         style="
+          gap: {gapSize}px;
           transform: translateX({offset}px);
           transition-duration: {durationMs}ms;
           transition-timing-function: {timingFunction};