Merge branch '18301-top-navigation-needs-hover-state' into 'master'

added hover state to top nav links

## What does this MR do?

Adds hover state to top nav links.

## Are there points in the code the reviewer needs to double check?

Ney.

## Why was this MR needed?

UX.

## What are the relevant issue numbers?

Closes #18301.

## Screenshots (if relevant)

![Screen_Shot_2016-06-07_at_23.23.45](/uploads/dac8ed99eca99fbcccbd98028e947ee1/Screen_Shot_2016-06-07_at_23.23.45.png)

See merge request !4521

app/assets/stylesheets/framework/nav.scss

@@ -347,6 +347,12 @@
       .badge {
         color: $gl-icon-color;
       }
+
+      &:hover {
+        a, i {
+          color: $black;
+        }
+      }
     }
   }