Add missing documentation about date and server header CLI options (encode#1194)

Author: Kludex

docs/settings.md

@@ -63,6 +63,8 @@ Note that WSGI mode always disables WebSocket support, as it is not supported by
 * `--proxy-headers` / `--no-proxy-headers` - Enable/Disable X-Forwarded-Proto, X-Forwarded-For, X-Forwarded-Port to populate remote address info. Defaults to enabled, but is restricted to only trusting
 connecting IPs in the `forwarded-allow-ips` configuration.
 * `--forwarded-allow-ips` <comma-separated-list> Comma separated list of IPs to trust with proxy headers. Defaults to the `$FORWARDED_ALLOW_IPS` environment variable if available, or '127.0.0.1'. A wildcard '*' means always trust.
+* `--server-header` / `--no-server-header` - Enable/Disable default `Server` header.
+* `--date-header` / `--no-date-header` - Enable/Disable default `Date` header.
 
 ## HTTPS