feat: add network magic as an optional init option

[raulduartep]

No description provided.

[luc10921]

As a suggestion, if you want to be clearer, you can also add a TSDoc on the init method to explain that we set validUntilBlock as 100 by default and do a getVersion rpc call to get the networkMagic if not passed

[ixje]

As a suggestion, if you want to be clearer, you can also add a TSDoc on the init method to explain that we set validUntilBlock as 100 by default and do a getVersion rpc call to get the networkMagic if not passed

to tag along on that, I think it's good to also mention it can throw an RpcError if fetching the network magic over RPC fails.