Adds the mutinynet signet (https://github.com/MutinyWallet/mutiny-net/) to the supported networks so it's possible to use it with Electrum. Mutinynet is similar to signet, except for a shorter block interval (30 sec), a nice faucet (faucet.mutinynet.com) and some extra features in its core fork. It also has some lightning network nodes, see the mempool instance on mutinynet.com.