Adds keyboard-mode outline to Checkbox

stylesheets/components/Checkbox.scss

@@ -9,6 +9,20 @@
     input {
       height: 18px;
       width: 18px;
+
+      @include mouse-mode {
+        &:focus,
+        &:active {
+          outline: none;
+        }
+      }
+
+      @include keyboard-mode {
+        &:focus,
+        &:active {
+          outline: 1px solid $color-ultramarine;
+        }
+      }
     }
   }