exclude menu and TOC items from the visited link styles for better UX (#4776)

* exclude menu and TOC items from the visited link styles for better UX

for better UX, menu and TOC items style should indicate only one thing, which is the current read item

* exclude nav items from the visited link styles for better UX

Author: Ahmed-Hakeem

website/src/css/custom.css

@@ -144,7 +144,7 @@ a.contents__link > code {
     color: var(--ifm-color-primary-lightest);
 }
 
-a:visited {
+a:visited:not(.menu__link, .table-of-contents__link, .navbar__link:not([target="_blank"])) {
   color: var(--ifm-color-primary);
 }
 .navbar .navbar__inner {
@@ -283,4 +283,4 @@ div[class*='announcementBar_'] {
   /* Intentionally override the theme behavior,
   so that the course banner image is effectively cropped*/ 
   z-index: calc(var(--ifm-z-index-fixed) -1) !important;
-}
+}