Updated global social media sprites to include mobile app icon

Author: cindyhuynh

Diff for: app/styles/partials/components.scss

@@ -382,6 +382,10 @@ a.hero-no-button > img {
   background-position: 0 -520px;
 }
 
+.social-list li.mobile {
+  background-position: 0 -560px;
+}
+
 /* Blockquote Footer Reset*/
 
 blockquote > footer {