nginx: add gzip_vary to recommended settings

Google PageSpeed recommends turning this on to allow proxies to cache

Changed files
+1
nixos
modules
services
web-servers
nginx
+1
nixos/modules/services/web-servers/nginx/default.nix
···
gzip_proxied any;
gzip_comp_level 9;
gzip_types text/plain text/css application/json application/javascript text/xml application/xml application/xml+rss text/javascript;
+
gzip_vary on;
''}
${optionalString (cfg.recommendedProxySettings) ''