lncfg+sample-lnd.conf: add DNS seed flag to chain cfg

sample-lnd.conf

@@ -417,6 +417,21 @@ bitcoin.node=btcd
 ; The CLTV delta we will subtract from a forwarded HTLC's timelock value.
 ; bitcoin.timelockdelta=40
 
+; The seed DNS server(s) to use for initial peer discovery. Must be specified as
+; a '<primary_dns>[,<soa_primary_dns>]' tuple where the SOA address is needed
+; for DNS resolution through Tor but is optional for clearnet users. Multiple
+; tuples can be specified, will overwrite the default seed servers.
+; The default seed servers are:
+;  mainnet:
+;    bitcoin.dnsseed=nodes.lightning.directory,soa.nodes.lightning.directory
+;    bitcoin.dnsseed=lseed.bitcoinstats.com
+;  testnet:
+;    bitcoin.dnsseed=test.nodes.lightning.directory,soa.nodes.lightning.directory
+;
+; Example for custom DNS servers:
+; bitcoin.dnsseed=seed1.test.lightning
+; bitcoin.dnsseed=seed2.test.lightning,soa.seed2.test.lightning
+
 ; Used to help identify ourselves to other bitcoin peers (default: neutrino).
 ; neutrino.useragentname=neutrino
 
@@ -589,6 +604,18 @@ litecoin.node=ltcd
 ; The CLTV delta we will subtract from a forwarded HTLC's timelock value.
 ; litecoin.timelockdelta=576
 
+; The seed DNS server(s) to use for initial peer discovery. Must be specified as
+; a '<primary_dns>[,<soa_primary_dns>]' tuple where the SOA address is needed
+; for DNS resolution through Tor but is optional for clearnet users. Multiple
+; tuples can be specified, will overwrite the default seed servers.
+; The default seed servers are:
+;  mainnet:
+;    litecoin.dnsseed=ltc.nodes.lightning.directory,soa.nodes.lightning.directory
+;
+; Example for custom DNS servers:
+; litecoin.dnsseed=seed1.test-ltc.lightning
+; litecoin.dnsseed=seed2.test-ltc.lightning,soa.seed2.test-ltc.lightning
+
 [Ltcd]
 
 ; The base directory that contains the node's data, logs, configuration file,