Gets a list of PEM encoded certificates to use with the
ssl_trusted_certificate parameter in nginx.
When using OCSP stapling with nginx, a file with a list of PEM encoded
certificates should be added to the ssl_trusted_certificate parameter.
Otherwise the ssl_stapling_verify parameter can't be enabled.
This program reads your certificate and any intermediate certificates in it.
It will use the CA Issuers - URI field for any remaining certificates in
the chain. When the field is empty it is assumed the root is reached.