feat: added prometheus metrics support

nginx.conf

@@ -1,3 +1,5 @@
+load_module modules/ngx_http_vhost_traffic_status_module.so;
+
 worker_processes  1;
 
 error_log stderr;
@@ -9,6 +11,7 @@ events {
 }
 
 http {
+  vhost_traffic_status_zone;
   include       mime.types;
   default_type  application/octet-stream;
   access_log    /dev/stdout;