add extra line before spacing utilities example

docs/components/utilities.md

@@ -37,6 +37,7 @@ Where *size* is one of:
 * `3` - (by default) for classes that set the `margin` or `padding` to `$spacer-x * 3` or `$spacer-y * 3`
 
 Here are some representative examples of these classes:
+
 ```scss
 .m-t-0 {
   margin-top: 0 !important;