Issue #2902956: Updated Varbase Installer to have a branded install.

themes/vartheme_admin/vartheme_admin.info.yml

@@ -22,3 +22,9 @@ regions_hidden:
 libraries:
   - 'vartheme_admin/global-admin-styling'
   - 'vartheme_admin/global-admin-scripts'
+  
+libraries-override:
+  seven/install-page:
+    css:
+      theme:
+        css/theme/install-page.css: css/install-page.css

themes/vartheme_admin/vartheme_admin.libraries.yml

@@ -2,7 +2,6 @@ global-admin-styling:
   css:
     theme:
       css/vartheme-admin.theme.style.css: {}
-      css/vartheme_admin_installer_page.css: {}
 global-admin-styling-rtl:
   css:
     theme: