www/nginx: add release note for nginx autoban feature

www/nginx/Makefile

@@ -1,5 +1,5 @@
 PLUGIN_NAME=		nginx
-PLUGIN_VERSION=		1.20
+PLUGIN_VERSION=		1.21
 PLUGIN_REVISION=	2
 PLUGIN_COMMENT=		Nginx HTTP server and reverse proxy
 PLUGIN_DEPENDS=		nginx

www/nginx/pkg-descr

@@ -8,6 +8,10 @@ reuse, SSL offload and HTTP media streaming.
 Plugin Changelog
 ================
 
+1.21
+
+* fix performance issue with autoban feature (contributed by jkellerer)
+
 1.20
 
 * User interface improvements of NAXSI configuration (contributed by 8191)