https://github.com/Behat/docs/blob/v3.0/user_guide/configuration.rst#extensions should cover all the options (namespaced class / automagic class / file path) supported by [ExtensionManager::instantiateExtension](https://github.com/Behat/Behat/blob/42f15e5d513fc10dd807f90379652bacd56930b6/src/Behat/Testwork/ServiceContainer/ExtensionManager.php#L176-L198) As identified in review for #146
https://github.com/Behat/docs/blob/v3.0/user_guide/configuration.rst#extensions should cover all the options (namespaced class / automagic class / file path) supported by ExtensionManager::instantiateExtension
As identified in review for #146