Fixed header bg color not being set in default (no) theme

Author: alexandrevryghem

src/app/header/header.component.scss

@@ -1,3 +1,7 @@
+header {
+  background-color: var(--ds-header-bg);
+}
+
 .navbar-brand img {
   max-height: var(--ds-header-logo-height);
   max-width: 100%;