Add support for 3rd-party login for Inoreader

[gracjankn]

In addition to being able to create an account with an e-mail and password, Inoreader supports registration and sign-in with via Apple, Google and Enterprise SSO.

I’d love to be able to use my account created via Sign in with Apple in NetNewsWire, but the app currently only supports Inoreader accounts created with an e-mail and password.

Unread and Fiery Feeds on the other hand both kick the user to the Inoreader website, where you can sign in using any method and authorize the app.

I wish NetNewsWire adopts this.