fix: enable SNI

[conradludgate]

👋 At Neon, we use SNI to know which database endpoint is being requested to connect to. Our fallback options are using options which this library also doesn't support, or using cleartext passwords and encoding the database endpoint into the password. See https://neon.tech/docs/connect/connection-errors#the-endpoint-id-is-not-specified

Reading https://forum.crystal-lang.org/t/specifying-the-sni-hostname-for-an-openssl-context/3872 it seems like enabling SNI wasn't too challenging. Testing locally it does seem to work.