Provide access to underlying PDO

[bfinlay]

The $app->db() method provided by foundation-core is very convenient to create a db instance from a dotenv configuration file. However, when you need to do something with the db connection that is not supported by PHP-DB, the only workaround is to create your own PDO connection and bypass the convenience of the $app->db().

Providing access to the PDO connect object would be useful when implementing features not supported by delight-im/PHP-DB.

The PDO connection object could be retrieved from the db object as needed for unsupported functionality, perhaps by $app->db()->getPdo()