Make lite validation also work properly for form select

Like validation was only work for form fields with the `.form-control` class. Selects
use the `.form-select` class. This change also applies lite validation for the selects.

src/scss/ui/forms/_validation.scss

@@ -6,4 +6,8 @@
   .form-control.is-#{$state}-lite {
     @extend %validation-lite;
   }
-}
\ No newline at end of file
+
+  .form-select.is-#{$state}-lite {
+    @extend %validation-lite;
+  }
+}