Add "offline_access" scope

[stevepanaghi]

As I'm rolling out tsidp across my home lab, I ran into a service(booklore) that it doesn't work with since tsidp doesn't support the "offline_access" scope. Can this be added in a future release?

[mostlygeek]

Note these are the currently supported scopes. One thing we could do here is allow a user configurable list of extraScopes. We currently do this with extraClaims.