Add export for WebStorageStateStore from oidc-client

[ryancole]

Makes sense to re-export this for users who need access to it.

[Powersource]

Maybe export the entire oidc-client default export? I'm finding myself also importing that to be able to do

Oidc.Log.logger = console;
Oidc.Log.level = Oidc.Log.DEBUG;

edit: #383

[simenandre]

@Powersource or @ryancole, is this something either of you could open a quick PR on? I think it makes sense to do this even though we have #652.

[simenandre]

Closing this as it's stale.