Add token object in addition to accessToken, to expose idToken and more

[dafnarosenblum]

Before the change, the hook exposed acessToken only. But by using auth0-spa-js, we're getting also the idToken, which is needed for cases we use Auth0 as an authorisation service that defines the rules for accessing data in our server / database.

This change allows externalizing other parameters in Auth0's response, such as idToken and the expiration of the token.

[corydeppen]

Is there opposition to including this or anything blocking it from being merged? I think it would be a helpful addition to the library, as there doesn't appear to be a way of accessing the id token at the moment.