Deprecation follow-ups

[lgarron]

Followups to #94 and #95 .

1. Mark the the package as deprecated on npm:

npm deprecate @github/webauthn-json "This package has been deprecated in favor of corresponding browser functionality. For more details, consult: https://github.com/github/webauthn-json"

2. Archive the project on GitHub.

[fletchto99]

Closing as this project has been deprecated. Please see the project readme for more information.