Spanish translation by Carlos Longarela (#526)

* Spanish translation by Carlos Longarela

* Added CI 2.0

* Add CodeCov; removing Docker files; fix cache

* Add clear log action; combine same errors in log; increase error log limit; fix offline assets/styles

* Add skip strategies setting and tests

* Add placeholder and additional documentation.

* Add filters for authorize URL and params, logout URL + tests

* Deleted users.php file

* initial-setup.css from https://github.com/auth0/wp-auth0/blob/master/assets/css/initial-setup.css

* Added 72 new translations

* Update es_ES.po

Translation feedback from our team.