fix: Library Preview Expand button covers dropdown (#1438)

src/library-authoring/LibraryAuthoringPage.scss

@@ -12,7 +12,7 @@
 }
 
 .library-authoring-sidebar {
-  z-index: 1001; // to appear over header
+  z-index: 1000; // same as header
   flex: 450px 0 0;
   position: sticky;
   top: 0;
@@ -21,6 +21,10 @@
   overflow-y: auto;
 }
 
+.dropdown-menu {
+  z-index: 1001; // over the sidebar
+}
+
 // Reduce breadcrumb bottom margin
 ol.list-inline {
   margin-bottom: 0;

src/library-authoring/component-info/ComponentPreview.tsx

@@ -55,7 +55,7 @@ const ComponentPreview = () => {
           variant="light"
           iconBefore={OpenInFull}
           onClick={openModal}
-          className="position-absolute right-0 zindex-10 m-1"
+          className="position-absolute right-0 zindex-1 m-1"
         >
           {intl.formatMessage(messages.previewExpandButtonTitle)}
         </Button>