* Don't require package tag or file comment inside src
* Removed package tag from files inside src
* Fixed tests directory in phpcs.xml.dist
* Fixed usage of package tag
* Fixed new classes
* Fixed coding standards
* Fixed coding standards in tests
* Add API endpoint to install themes
* Add API endpoint to activate a theme
* Add an array of allowed themes and sanitize slugs
* Limit allowed themes to already installed or free themes
* Add theme installation tests
* Add tests for theme activation
* Add onboarding theme installation and activation tests
* Remove unused argument in onboarding plugins API