Add missing background for CORE-292

Author: jmgasper

src/shared/components/challenge-detail/Header/style.scss

@@ -18,6 +18,12 @@
   font-size: 12px;
   font-family: 'Roboto', sans-serif;
   line-height: 1.2em;
+  background-color: $tc-gray-20;
+  padding-left: 20px;
+  padding-right: 30px;
+  padding-bottom: 10px;
+  padding-top: 10px;
+  border-radius: 4px;
 
   a {
     color: $tc-dark-blue;