Merge pull request #349 from ember-learn/use-variable-for-hr-margin

using a spacing variable for hr margin

Author: jaredgalanis

addon/styles/global.css

@@ -224,7 +224,7 @@ code {
 hr {
   background: var(--color-gray-300);
   border: 1px var(--color-gray-300);
-  margin: 35px 0px;
+  margin: var(--spacing-4) 0px;
   border-radius: 1px;
   height: 2px;
 }