Update Angular to Angular 18

[frederikprijck]

As per the supported versions of Angular, anything < 18 is no longer supported by google. As called out in our readme, we only support versions of Angular that are actively supported, so we are updating Angular 13 to 18.

This also obsoletes #673, as core-js nolonger is in-use:

❯ npx npm-why core-js

  No one requires core-js.

❯ npm ls core-js
auth0-angular@0.0.0 /Users/frederikprijck/Development/auth0/auth0-angular
└── (empty)

Also moved CI to use Node 22. Additionally the unit tests also run on 20.

[kishore7snehil]

LGTM!