update docs

Author: Snawoot

README.md

@@ -493,6 +493,10 @@ Usage of /home/user/go/bin/dumbproxy:
     	timeout for shared resolves of DNS cache (default 5s)
   -dns-cache-ttl duration
     	enable DNS cache with specified fixed TTL
+  -dns-prefer-address value
+    	address resolution preference (none/ipv4/ipv6) (default ipv4)
+  -dns-server value
+    	nameserver specification (udp://..., tcp://..., https://..., tls://..., doh://..., dot://..., default://). Option can be used multiple times for parallel use of multiple nameservers. Empty string resets the list
   -hmac-genkey
     	generate hex-encoded HMAC signing key of optimal length
   -hmac-sign

main.go

@@ -383,7 +383,7 @@ func parse_args() CLIArgs {
 	flag.Int64Var(&args.bwBurst, "bw-limit-burst", 0, "allowed burst size for bandwidth limit, how many \"tokens\" can fit into leaky bucket")
 	flag.UintVar(&args.bwBuckets, "bw-limit-buckets", 1024*1024, "number of buckets of bandwidth limit")
 	flag.BoolVar(&args.bwSeparate, "bw-limit-separate", false, "separate upload and download bandwidth limits")
-	flag.Func("dns-server", "nameserver specification (udp://..., tcp://..., https://..., tls://..., doh://..., dot://..., default://). Option can be used multiple times for parallel use of multiple nameservers. Empty string resets list", func(p string) error {
+	flag.Func("dns-server", "nameserver specification (udp://..., tcp://..., https://..., tls://..., doh://..., dot://..., default://). Option can be used multiple times for parallel use of multiple nameservers. Empty string resets the list", func(p string) error {
 		if p == "" {
 			args.dnsServers = nil
 		} else {