Polylang Pro 3.6.5

* Security: Fix categories and media duplication not protected from CSRF
* Pro: Allow to update the plugin with WP CLI
* Pro: Fix search in the button block not filtered in the correct language (needs WP 5.1)
* Add Saraiki to the predefined languages list
* Fix a conflict causing a blank page with Divi

* Add compatibility with WP 5.0
* Fix custom flags when the WP content folder is not in the WP install folder
* Fix PHP notice if a language has no flag