message: doc: add signet to share/examples/bitcoin.conf
diff: # Network-related settings:
  -# Note that if you use testnet or regtest, particularly with the options
  +# Note that if you use testnet, signet or regtest, particularly with the options
  # addnode, connect, port, bind, rpcport, rpcbind or wallet, you will also
  # want to read "[Sections]" further down.
  -# Run on the test network instead of the real bitcoin network.
  +# Run on the testnet network
  #testnet=0
  +# Run on a signet network
  +#signet=0
  +
  # Connect via a SOCKS5 proxy
  #proxy=127.0.0.1:9050
  # Listening mode, enabled by default except when 'connect' is being used
  #listen=1
  -# Port on which to listen for connections (default: 8333, testnet: 18333, regtest: 18444)
  +# Port on which to listen for connections (default: 8333, testnet: 18333, signet: 38333, regtest: 18444)
  #port=
  # Maximum number of inbound+outbound connections.
  @@ -140,7 +143,7 @@ rpcport=9902
  #minimizetotray=1
  # [Sections]
  -# Most options apply to mainnet, testnet and regtest.
  +# Most options apply to mainnet, testnet, signet and regtest.
  # If you want to confine an option to just one network, you should add it in the
  # relevant section below.
  # EXCEPTIONS: The options addnode, connect, port, bind, rpcport, rpcbind and wallet
  @@ -152,5 +155,8 @@ rpcport=9902
  # Options only for testnet
  [test]
  +# Options only for signet
  +[signet]
  +
  # Options only for regtest
  [regtest]
  