Indicate admins in the group member list with a sheriff badge

src/groups.js

@@ -36,6 +36,7 @@ export function groupMemberFromApiObject(apiObject) {
         userId: apiObject.user_id,
         displayname: apiObject.displayname,
         avatarUrl: apiObject.avatar_url,
+        isAdmin: apiObject.is_admin,
     };
 }