Enable email/password and token authentication

[SpinningCubeSolutions]

Hi, I'm currently using a fork of this plugin which enables token-based authentication by submitting a username and password. However, I think that this feature should be part of the main plugin, particularly when the fork is less frequently updated than the original repo.

I'm using the API to create an app that allows customers to browse products from the store, and in this context it makes sense that the customers can login with email and password and receive a token that is stored on the device and can be sent with the API requests. Having to add users manually before they can use the API makes no sense.