Add healthcheck endpoint

nginx.conf

@@ -9,6 +9,11 @@ server {
     gzip_min_length 1024;
     gzip_types text/plain text/css application/javascript application/json image/svg+xml;
 
+    location = /healthcheck {
+        add_header Content-Type application/json;
+        return 200 'ok';
+    }
+
     location /assets/ {
         expires 1y;
         add_header Cache-Control "public, immutable";