An idea that came up in https://caddy.community/t/save-internally-issued-wildcard-certificate-in-consul/11740, this a simple module that might be useful for anyone who uses storage modules that aren't filesystem, to let them load certs/keys externally issued for use by Caddy.
Bit goofy, since we need to fetch the certmagic.Storage during provisioning, it needs a wrapping struct instead of just being an array like `load_files`.
Future work might involve adding Caddyfile support via a subdirective of the `tls` directive maybe?
