Support for filters

Thanks a lot for this module, saved my day :) I'm using this when listing Webform open/close dates, as Webforms are config entities and do not provide almost any decent way to format the output besides tweaking the output with Twig. I did have to swap the $value = $values->{$this->view->storage->get('base_table') . '_' . $timestamp_field}; part to just use strtotime with $values->{$timestamp_field}) instead of $view->storage values, but otherwise this works out of the box for it.

Would it be possible to get similar "global timestamp" functionality for filters? I was able to get a custom filter to show up, but I just can't get the filter to actually do any filtering. The Webform open/close dates are stored in config in format of Y-m-d\TH:i:s and I guess that's why I just can't get it working myself as the basic string filter just isn't doing it. It would be amazing to get some filtering done with the same module!