allow custom stream conf

Allow a top-level custom `stream` configuration file to be loaded.

docker/rootfs/etc/nginx/nginx.conf

@@ -84,6 +84,9 @@ http {
 stream {
 	# Files generated by NPM
 	include /data/nginx/stream/*.conf;
+
+	# Custom
+	include /data/nginx/custom/stream[.]conf;
 }
 
 # Custom