Add option for non-tls operation

[Zapeth]

I've been trying to set up a Linux server <=> Windows clients environment but every time I try to connect with a client I get:
Error: Failed to connect: The certificate's CN name does not match the passed value. (os error -2146762481)
(error constant name: CERT_E_CN_NO_MATCH)

I've already tried generating various certificates with different altNames (IP and DNS) but nothing worked.

I realize this is probably not an issue with this crate, but I'd still like to request an option to run the server without requiring a certificate.

For a quick and dirty workaround I disabled

rkvm/client/src/main.rs

Lines 34 to 37 in bf13366

	let mut stream = connector
	.connect(server, stream)
	.await
	.context("Failed to connect")?;

and

rkvm/server/src/main.rs

Lines 85 to 91 in bf13366

	let stream = match acceptor.accept(stream).await {
	Ok(stream) => stream,
	Err(err) => {
	log::error!("{}: TLS error: {}", address, err);
	continue;
	}
	};

, but a proper configurable implementation would be obviously preferred.