Get access token about active-directory-b2c-dotnetcore-webapp

[gsacavdm]

We'll update this sample in the next few weeks to do access tokens properly which involves a very different approach. This approach involves using access tokens rather than the id_token (no more SaveSigninToken and Bootstrap context). To do this you'll need:

1. Register your web api and define scopes for it
2. In your web app's registration, indicate that you want to consume those scopes.
3. Change your web app's OpenID Connect middle ware:
   1. Response type of "id_token code"
   2. Scope of "openid {your-web-api-scopes}"
4. Finally, you'll use MSAL in the OnAuthorizationCodeReceived event to redeem the code for an access token.

[gsacavdm]

See #16

[gsacavdm]

The sample has been updated with support for access tokens (readme update pending though).