nginx.conf: add simple default_server (needed)

contrib/nginx.conf

@@ -1,3 +1,13 @@
+server {
+	listen 80 default_server;
+	listen [::]:80 default_server;
+	server_name _;
+
+	location / {
+		return 303 http://maszt.5g/;
+	}
+}
+
 server {
 	listen 80;
 	listen [::]:80;