Avoid HTTPS requirement for local network testing

[decentral1se]

Report coming from testing for #355:

I can tunnel the machine locally, but I think the whole https-domain thing stops me from being able to test without a public address with https.

I think we could disable the https requirement if we tweaked:

go-ssb-room/cmd/server/main.go

Lines 149 to 154 in 00a1452

	if httpsDomain == "" {
	if !development {
	return fmt.Errorf("https-domain can't be empty. See '%s -h' for a full list of options", os.Args[0])
	}
	httpsDomain = "localhost"
	}

Maybe some other stuff needs changing then. It'd be nice to not have to deal with this so local network testing is much easier

/cc @luandro

[decentral1se]

Another take on this is: document how to have https -> internet on a local setup 🙃 Some tunneling setup that doesn't require going all in on explaining port forwarding on your local router and such (down the rabbit hole for the docs...). I wonder would an alliance with https://greenhouse.server.garden be useful for this 🤔