docs: Enhance table of contents link style with underline

Author: clicktodev

website/src/css/customTheme.scss

@@ -1503,6 +1503,7 @@ div[class^="tableOfContents"] {
   .table-of-contents__link--active {
     font-weight: 500;
     color: var(--home-button-primary) !important;
+    text-decoration: underline;
 
     code {
       font-weight: 700;