Add a permissive CORS header on the assets directory

docker/nginx/conf.d/default.conf

@@ -17,6 +17,11 @@ server {
         add_header Cache-Control no-cache;
     }
 
+    # CORS (for third-party integrations)
+    location /assets/ {
+        add_header Access-Control-Allow-Origin *;
+    }
+
     # Block access to the file used for screenshots
     location = /screenshots.html {
         internal;