multi: add signet parameters

With this commit we make lnd compatible with the public signet test
network.

lncfg/chain.go

@@ -13,10 +13,13 @@ type Chain struct {
 
 	Node string `long:"node" description:"The blockchain interface to use." choice:"btcd" choice:"bitcoind" choice:"neutrino" choice:"ltcd" choice:"litecoind"`
 
-	MainNet  bool `long:"mainnet" description:"Use the main network"`
-	TestNet3 bool `long:"testnet" description:"Use the test network"`
-	SimNet   bool `long:"simnet" description:"Use the simulation test network"`
-	RegTest  bool `long:"regtest" description:"Use the regression test network"`
+	MainNet         bool     `long:"mainnet" description:"Use the main network"`
+	TestNet3        bool     `long:"testnet" description:"Use the test network"`
+	SimNet          bool     `long:"simnet" description:"Use the simulation test network"`
+	RegTest         bool     `long:"regtest" description:"Use the regression test network"`
+	SigNet          bool     `long:"signet" description:"Use the signet test network"`
+	SigNetChallenge string   `long:"signetchallenge" description:"Connect to a custom signet network defined by this challenge instead of using the global default signet test network -- Can be specified multiple times"`
+	SigNetSeedNode  []string `long:"signetseednode" description:"Specify a seed node for the signet network instead of using the global default signet network seed nodes"`
 
 	DefaultNumChanConfs int                 `long:"defaultchanconfs" description:"The default number of confirmations a channel must have before it's considered open. If this is not set, we will scale the value according to the channel size."`
 	DefaultRemoteDelay  int                 `long:"defaultremotedelay" description:"The default number of blocks we will require our channel counterparty to wait before accessing its funds in case of unilateral close. If this is not set, we will scale the value according to the channel size."`