New TypeScript typings don't allow optionless UserManager

[ulrichb]

Since 1.10 the following code ...

const userManager = new Oidc.UserManager({});
userManager.signinSilentCallback()
    .catch(e => { console.error("Error while handling silent signin", e); });

... compiles to ...

Argument of type '{}' is not assignable to parameter of type 'UserManagerSettings'.
Type '{}' is missing the following properties from type 'UserManagerSettings': authority, client_id

For the signinSilentCallback() it is not necessary to provide authority/client_id.
(See https://github.com/IdentityModel/oidc-client-js/blob/dev/samples/VanillaJS/public/identityserver-sample-silent.js.)

[brockallen]

So then what's the fix? Send a PR, please?

[ulrichb]

=> #1018