Add a feature flag for loading new CSS stylesheets

app/config/sculpin_site.yml

@@ -30,6 +30,9 @@ drupalorg:
   url: https://www.drupal.org/u/%drupalorg.username%
   username: opdavies
 
+features:
+  new_css: true
+
 github:
   url: https://github.com/%github.username%
   username: opdavies

app/config/sculpin_site_prod.yml

@@ -2,6 +2,9 @@
 imports:
   - sculpin_site.yml
 
+features:
+  new_css: false
+
 url: https://www.oliverdavies.uk
 
 use_transistor: false