* Create an auth exchange and implement adding token to auth header

* Add tests for the auth exchange

* Expose api to add auth to operation instead of just the header

* Add auth attempt to operation and trigger refresh

* Update auth exchange to combine getAuth and getInitialAuthState

* Refactor auth exchange and account for teardown operations

* Add error excahnge to auth exchange readme

* Replace AuthConfig<T> with documented interface

* Deduplicate operations in the authExchange queue

* Update import in authExchange to rely on @urql/core

* Add a mutate method to the authExchange's getAuth params

* Delay initial getAuth by one tick to wait for result$

Avoid calling getAuth before the rest of the exchange has
completely run.

* Update tests and test for mutate() method

* Add test for didAuthError method

* Add test for willAuthError

* Update authExchange api documentation

* Target es2019 for optional chaiining

* Update auth exchange initial version to v0.1.0

* Fix readme
Co-authored-by: Phil Pluckthun <phil@kitten.sh>