feat: react to docker network connect/disconnect event

app/Procfile

@@ -1,2 +1,2 @@
-dockergen: docker-gen -watch -notify "nginx -s reload" /app/nginx.tmpl /etc/nginx/conf.d/default.conf
+dockergen: docker-gen -watch -wait 100ms:500ms -event-filter event=connect -event-filter event=disconnect -notify "nginx -s reload" /app/nginx.tmpl /etc/nginx/conf.d/default.conf
 nginx: nginx -g "daemon off;"