Add CORS headers for Garage web access

Fixes Discourse plugin JS usage

site-cookbooks/kosmos_garage/templates/nginx_conf_web.erb

@@ -18,6 +18,7 @@ server {
   }
 
   location / {
+    add_header 'Access-Control-Allow-Origin' '*' always;
     proxy_intercept_errors on;
     proxy_cache garage_cache;
     proxy_pass http://garage_web;