Documentation: Include reference to onelogin/php-saml advanced settings (contactPerson, Organization)

[markfullmer]

Summary

The onelogin/php-saml library supports passing advanced settings, as described in https://github.com/SAML-Toolkits/php-saml?tab=readme-ov-file#settings

The documentation for wp-saml-auth should include at least a link to this documentation for reference. Alternatively, the wpsax_filter_option example snippet could be updated to include more of the advanced settings.