Added support for changing the color of the navbar

Author: alexandrevryghem

src/app/navbar/expandable-navbar-section/expandable-navbar-section.component.scss

@@ -6,6 +6,7 @@
 }
 
 .dropdown-menu {
+    background-color: var(--ds-navbar-bg);
     overflow: hidden;
     min-width: 100%;
     border-top-left-radius: 0;

src/app/navbar/navbar.component.scss

@@ -1,4 +1,5 @@
 nav.navbar {
+    background-color: var(--ds-navbar-bg);
     border-bottom: 1px var(--ds-header-navbar-border-bottom-color) solid;
     align-items: baseline;
 }

src/styles/_custom_variables.scss

@@ -24,6 +24,7 @@
   --ds-header-logo-height-xs: 50px;
   --ds-header-icon-color: #{$link-color};
   --ds-header-icon-color-hover: #{$link-hover-color};
+  --ds-navbar-bg: var(--ds-header-bg);
   --ds-header-navbar-border-top-color: #{$white};
   --ds-header-navbar-border-bottom-color: #{$gray-400};
   --ds-navbar-link-color: #{$cyan};

src/themes/dspace/app/navbar/navbar.component.scss

@@ -4,6 +4,10 @@ nav.navbar {
   align-items: baseline;
 }
 
+.navbar-nav {
+  background-color: var(--ds-navbar-bg);
+}
+
 /** Mobile menu styling **/
 @media screen and (max-width: map-get($grid-breakpoints, md)-0.02) {
   .navbar {