Support certificate reloading without exposing NIO #35
Description
Support for certificate reloading is currently available by initializing the TransportSecurity configuration with a CertificateReloader conformance.
CertificateReloader is defined in the NIOCertificateReloading product from swift-nio-extras, which transitively depends on NIO. Given that the goal of this package is to not expose NIO types, we should fix this.
See #34 (comment) for context and broader discussion.