Add support for NC 18

[bekon16]

Hi,

Is this version compatible with NC18?
https://apps.nextcloud.com/apps/ocdownloader - the last one here is only 17.

Cant upgrade without ocDownloader :)

[e-alfred]

This line of code currently breaks ocDownloader on Nextcloud 18:

ocdownloader/controller/index.php

Line 247 in f5f4ae9

$scanner = new \OC\Files\Utils\Scanner($user, \OC::$server->getDatabaseConnection(), \OC::$server->getLogger());

[e-alfred]

Fixed by @mamartel, I will publish a new release soon.