style: highlight scrollbar on hover and change scrollbar width as thin (#137)

Author: razonyang

assets/hb/modules/code-block-panel/scss/index.scss

@@ -1,4 +1,14 @@
 /*! purgecss start ignore */
 @import "../../../../mods/code-block-panel/scss/index";
 
+.highlight {
+  pre {
+    scrollbar-width: thin;
+
+    &:hover {
+      scrollbar-color: var(--#{$prefix}primary) transparent;
+    }
+  }
+}
+
 /*! purgecss end ignore */