This commit updates README and docs folder that not updated on
how can an offer be made and how LNDK now can use other data path
for storing logs and TLS certs.
This PR autogenerates TLS credentials in LNDK's data dir at ~/.LNDK and
requires TLS to be used when connecting to the gRPC server.
Some of this code took inspiration from CLN and TEOS's gRPC servers, so credit
where it's due.
