Handle authentication when Wordpress REST API is not public

[jessicaribeiroalves]

Not really an issue, this is more like an improvement suggestion. It would be helpful to have a piece of authentication handling in cases the Wordpress REST API is not public.

Expected Behavior

Authentication handling would allow people to use the plugin even when the Wordpress REST API is not public.

Current Behavior

Currently the plugin doesn't handle authentication so you're able to use it only with public Wordpress REST APIs.

Steps to Reproduce

Run the migration script and get a 401: Unauthorized when trying to access the Wordpress REST API that isn't publicly available.

[jessicaribeiroalves]

Possible solution: #17