Support for signet

[bodymindarts]

We would like to run our staging environment on signet and are running into ExpectedLndWithKnownChain coming from this library.

I'm trying to figure out what is the correct patch to apply don't quite understand this line.

The lmcli return from getinfo contains:

    "chains": [
        {
            "chain": "bitcoin",
            "network": "signet"
        }
    ],

Which doesn't really match with the reverseBytes stuff that is being used here.

Any help is appreciated!

[alexbosworth]

networks are defined here
https://github.com/alexbosworth/ln-sync/blob/master/chain/networks.json

add the block hash identifier for the network, this is for the bolts https://github.com/lightning/bolts/blob/master/00-introduction.md#chain_hash