Design: Improved Low visibility and contrast in sidebar (#2432)

* change colors

* added navGroupSubcategoryTitleColor

* Add a new line at the end of file

Co-authored-by: Himanshu Mishra <himanshu@orkohunter.net>

microsite/static/css/custom.css

@@ -113,6 +113,10 @@ td {
   color: $navigatorTitleTextColor;
 }
 
+.toc .toggleNav .navGroup .navGroupSubcategoryTitle {
+  color: $navGroupSubcategoryTitleColor;
+}
+
 .toc .toggleNav ul li a,
 .onPageNav a {
   color: $navigatorItemTextColor;