Create the file_extension_register interface. This should have:
- A method register_extensions which returns all extensions supported by the implementing class, and their lang string descriptors. E.g. [‘png’ => ‘what is going to happen when this module processes the png’]. This could be an array or a formal object - time permitting.
- Note: objects in plugins only implement this contract when they want to support at least one file extension, however, we need to provide a way that this method can return ‘all known extensions’. Whether that be via a special extension ‘*’ or some other return is up for discussion.