Support FTP over explicit TLS

[com6056]

Description

👋 First off, thanks so much for the awesome project! 🎉

Right now it looks like if you enable TLS, we only use DialWithTLS.

Some FTP servers require a separate explicit TLS setting though which seems as easy as just using DialWithExplicitTLS.

It would be great to add a separate (mutually exclusive from tls) config flag, maybe named explicitTLS, that would useDialWithExplicitTLS instead.

Thanks! 🙌