nginx configuration: use more than one process

roles/matrix-nginx-proxy/templates/nginx/nginx.conf.j2

@@ -8,7 +8,7 @@
 # - various temp paths are changed to `/tmp`, so that a non-root user can write to them
 # - the `user` directive was removed, as we don't want nginx to switch users
 
-worker_processes 1;
+worker_processes auto;
 
 error_log /var/log/nginx/error.log warn;
 pid /tmp/nginx.pid;