remame sendfile to send_file and senddir to send_dir apparently, on some systems there is a sendfile(2), so to avoid a name clash we rename it to send_file and send_dir.

explicitly require TLS 1.2 or 1.3 it's the default, but just in case (since gemini spec explicitly talks about 1.3 as "default" and 1.2 for ease of implementation)

initial commit