MC-943: Grouping content blocks and containers in the Panel

- style scrollbar

Author: anthoula

app/code/Magento/PageBuilder/view/adminhtml/web/css/source/_page-builder.less

@@ -50,6 +50,14 @@
                 height: 100vh;
                 overflow-y: auto;
 
+                &::-webkit-scrollbar {
+                    width: 5px;
+                }
+
+                &::-webkit-scrollbar-thumb {
+                    background-color: darkgrey;
+                }
+
                 .pagebuilder-panel-groups {
                     padding-bottom: 41px;
                 }