Add z-index to scroller's content and shadows (#1338)

* add z-index to content and shadows; fixes #1326

* remove unused property

packages/webawesome/docs/docs/resources/changelog.md

@@ -26,6 +26,7 @@ Components with the <wa-badge variant="warning">Experimental</wa-badge> badge sh
 - Fixed a bug in JSX typings that prevented the types file from being exported [pr:1295]
 - Fixed a bug in JSX typings that generated the incorrect component imports [issue:1303]
 - Fixed a bug in `<wa-slider>` that prevented the thumb from receiving focus when clicking/tapping [issue:1312]
+- Fixed a bug in `<wa-scroller>` that caused the shadow to appear below relatively-positioned elements [issue:1326]
 
 ## 3.0.0-beta.4
 

packages/webawesome/src/components/scroller/scroller.css

@@ -20,6 +20,7 @@
 }
 
 #content {
+  z-index: 1; /* below shadows */
   border-radius: inherit;
   scroll-behavior: smooth;
   scrollbar-width: thin;
@@ -102,6 +103,7 @@
   #start-shadow,
   #end-shadow {
     position: absolute;
+    z-index: 2;
     right: 0;
     left: 0;
     height: var(--shadow-size);