AlternativeVerticals: add :focus styling to links (#1063)

* AlternativeVerticals: add :focus styling to links

This commit adds default :focus styling to the vertical
and universal links.

J=SLAP-588
TEST=manual

Check that I can tab over to the links, and they will show the new
styling when tabbed over to.

test that if I change the focus color to pink, the pink takes priority
over the regular text color

src/ui/sass/modules/_AlternativeVerticals.scss

@@ -78,7 +78,7 @@ $alternative-verticals-emphasized-font-weight: var(--yxt-font-weight-medium) !de
       margin-right: 5px;
     }
 
-    &:hover {
+    &:hover, &:focus {
       .yxt-AlternativeVerticals-suggestionLink--copy {
         text-decoration: underline;
       }
@@ -105,7 +105,7 @@ $alternative-verticals-emphasized-font-weight: var(--yxt-font-weight-medium) !de
   &-universalLink {
     text-decoration: none;
 
-    &:hover {
+    &:hover, &:focus {
       text-decoration: underline;
     }
   }